UNIVERSITY   OF  CALIFORNIA   PUBLICATIONS 

IN 

AGRICULTURAL    SCIENCES 

Vol.  2,  No.  4,  pp.  81-190,  plates  22-35  No%'ember    24,  1919 


MUTATION  IN  MATT  III  OLA' 


BY 

HOWARD  B.  FROST 


CONTENTS 

PAGE 

Introduction 81 

Genetic  literature  relating  to  Matthiola  84 

Methods    85 

Experimental  data  89 

The  occurrence  of  apparent  mutants  89 

Characteristics  and  heredity  of  mutant  types  92 

1.  The  early  type  92 

2.  The  smooth-leaved  type 118 

3.  The  large-leaved  type  125 

4.  The  crenate-leaved  type  127 

5.  The  slender  type  135 

6.  The  narrow-leaved  type  141 

7.  Miscellaneous  aberrant  types  143 

8.  Some  probabilities  of  random  sampling 145 

General  discussion  153 

Summary    159 

Literature  cited 161 


INTRODUCTION 

It  is  hardly  safe  to  use  the  term  mutation  without  first  defining  it. 
In  this  paper  it  will  be  taken  to  mean  a  genotypic  change,  or  a  change 
in  essential  hereditary  constitution,  due  neither  to  immediate  cross 
fertilization  nor  to  segregation  in  a  heterozygous  parent.  No  attempt 
will  be  made  to  restrict  the  term  to  any  of  the  known  or  supposed 
types  of  such  genotypic  change ;  a  limitation  of  this  kind,  which 
restricts  the  generally  accepted  sense  of  a  widely  used  term,  seems  to 
tend  to  confusion  rather  than  to  clearness. 


1  Paper    no.    52,    University    of   California    Citrus    Experiment    Station    and 
Graduate  School  of  Tropical  Agriculture,  Riverside,  California. 


82  University  of  California  Publications  in  Agricultural  Sciences        [Vol.  4 

If  we  use  the  term  factor  mutation,2  (Babcock,  1918)  where  the 
cytological  change  occurs  within  a  locus,  transforming  a  factor  into  a 
different  factor,  two  analogous  terms  will  apply  where  the  cytological 
change  is  external  to  the  locus.  When  the  cytological  change  consists 
of  a  loss,  reduplication,  or  transposition  of  one  or  more  loci  it  may 
be  called  a  locus  mutation,  and  when  the  change  consists  in  such 
phenomena  affecting  a  whole  chromosome  it  may  be  called  a  chromo- 
some mutation.  If  the  term  mutation  is  applied  to  the  cytological 
change  itself,  the  last  two  types  of  mutation  may  be  grouped  together 
as  extralocus  mutations,  while  the  first  type  consists  of  intralocus 
mutations.  Examples  of  factor  mutation  are  white  eye  in  DrosopJiila, 
and  probably  the  rubrinervis  type  in  Oenothera;  an  example  of  locus 
mutation  is  (possibly)  "deficiency"  in  DrosopJiila ;  and  examples  of 
chromosome  mutation  are  Oenothera  gigas  and  0.  lata. 

It  is  now  evident  that  the  immediate  problem  with  Oenothera  relates 
to  the  mechanism  of  heredity  in  the  genus.  There  are  two  sharply 
opposed  views.  One  is  that  recently  emphasized  by  Atkinson  (1917, 
p.  254),  when  he  says,  "The  evidence  from  Oenothera  cultures  points 
more  and  more  to  the  conclusion  of  Shull  that  'a  hereditary  mechanism 
must  exist  in  Oenothera  fundamentally  different  from  that  which  dis- 
tributes the  Mendelian  unit-characters.'  "  The  opposing  view  is 
represented  by  Muller's  (1918)  strictly  Mendelian  explanation  for 
Oenothera,  based  on  "an  OenotJi  era-like  case  in  Drosophila" ;  he  says, 
"The  striking  parallel  between  the  above  behavior  and  that  exhibited 
in  Oenothera  makes  it  practically  certain  that  this,  too,  is  a  complicated 
case  of  balanced  lethal  factors." 

A  notable  feature  of  the  extensive  genetic  study  of  Oenothera  is 
the  lack  of  progress  toward  any  definitely  supported  explanation  of 
its  hereditary  mechanism  which  is  not  Mendelian.  The  only  definite 
non-Mendelian  hypothesis  of  chromosome  behavior  so  far  proposed, 
aside  from  "merogony"  and  other  hypotheses  (Goldschmidt,  1916) 
apparently  possible  but  not  proved  for  Oenothera,  which  assume  loss 
of  chromatin  after  fertilization,  seems  to  be  Swingle's  (1911) 
"zygotaxis, "  proposed  for  the  apparently  parallel  case  of  Citrus. 
This  suggestion  that  Fx  hybrids  may  differ,  apart  from  non-uniformity 
of  the  Pj  gametes,  because  of  the  establishment  of  permanently  differ- 
ent arrangements  of  the  chromosomes  in  the  fertilized  egg,  still  seems 
to  be  purely  speculative. 

With  more  or  less  "Oenoth  era-like"  cases  in  other  genera,  the  only 
definite  progress  in  analysis  seems  to  have  resulted  from  the  assump- 


2  Muller  (1918)  has  recently  used  point  mutation  in  the  same  sense. 


L91UJ  Frost:    Mutation  m  Uatthiola  83 

t ion  of  Mendelian  segregation.     With  Oenothera  itself,  the  trend  of 

the  evidence  tends  to  favor  tins  form  of  explanation. 

This  fact  is  strikingly  illustrated  by  two  papers  of  de  Vries  i  L918, 
L919)  which  have  appeared  since  the  presenl  paper  was  written, 
especially  as  .Midler's  (1918)  complete  report  on  the  beaded-wing 
case  in  Drosophila  (see  especially  pp.  471-474,  48!),  and  498-499) 
indicates  that  de  Vries  had  hardly  yet  realized  the  full  possibilities  of 
the  balanced-factor  hypothesis.  In  the  light  of  Midler's  masterly 
demonstration  of  these  possibilities,  we  may  be  confident  that  "mass 
mutation"  is  merely  ordinary  segregation,  and  that  the  "unisexual" 
crosses  of  Oenothera  are  really  "Mendelian"  in  their  essential  phe- 
nomena. Some  difference  of  usage  respecting  the  inelusiveness  of 
the  term  M<  mli  Han  may  be  involved  here,  it  is  true,  since  apparently 
de  Vries  would  apply  it  only  to  cases  where  "strictly  homologous  factors 
are  opposed  in  homologous  chromosomes.  Since,  however  (M idler, 
1918),  there  are  good  reasons  for  expecting  the  occurrence  of  grada- 
tions of  similarity  and  of  synaptic  attraction  between  opposed  loci,  and 
hence  of  gradations  of  linkage,  the  criterion  of  Mendelian  behavior 
should  obviously  be  the  occurrence  of  segregation  between  homologous 
chromosomes,  whatever  their  degree  of  similarity  or  amount  of  cross- 
ing over.  We  have  no  reason  to  assume  that  an  "unpaired"  factor 
in  a  parent  would  so  divide  as  to  be  included  in  all  gametes;  on  the 
other  hand,  we  have  learned  of  a  mechanism  capable  of  insuring,  in 
certain  particular  cases,  the  inclusion  of  a  certain  factor  or  group  of 
factors  either  in  every  functional  gamete  or  in  every  viable  zygote. 

No  doubt,  a.s  Davis  (1917)  says,  "A  great  forward  step  will  be 
taken  in  Oenothera  genetics  when  types  of  proven  purity  have  been 
established  ....."  Meanwhile,  cases  of  "Oenothera-like"  heredity  in 
species  known  to  possess  the  Mendelian  mechanism  deserve  most 
thorough  investigation.  Special  interest  consequently  attaches  to  the 
peculiar  inheritance  of  certain  apparent  mutations  of  the  ten-weeks 
stock  (Matthiola  annua  Swreet),  a  species  in  which  various  character- 
istics are  typically  Mendelian.  A  remarkable  series  of  aberrant  forms 
in  this  species3  has  been  briefly  discussed  in  two  preliminary  com- 
munications (Frost,  1912  and  1916),  and  the  present  paper  gives  a 
fuller  account  of  the  same  phenomena.4 


3  In  the  variety  "Snowflake, "  a  glabrous,  double-producing  form  with  white 
flowers. 

*  While  this  paper  was  in  press  Blakeslee  and  Avery  (1019),  have  reported 
the  occurrence  of  apparent  mutations  in  Datura,  which  seem  to  be  similar  in 
almost  every  respect  to  those  here  discussed. 


84  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

Apparent  mutants  were  first  found  in  the  course  of  work  on 
another  problem,  the  relation  of  temperature  to  variation  (Frost, 
1911),  conducted  at  Cornell  University.  Studied  incidentally  at 
first,  these  new  forms  were  later  given  special  attention.  About  nine 
thousand  plants,  of  which  about  two  thousand  were  progeny  of 
mutant-type  parents  of  peculiar  heredity  (nearly  one-fourth  of  the 
latter  representing  crosses  with  Snowflake),  have  been  examined 
altogether.  Some  of  these  plants  have  been  grown  at  Riverside,  where 
hybridization  studies  with  mutant  types  are  in  progress.  The  present 
account  considers  the  origin  and  characteristics  of  these  types,  their 
inheritance  with  self  pollination,  and  the  rather  meager  available  data 
relating  to  their  behavior  in  crossing. 

In  connection  with  the  work  at  Cornell,  special  acknowledgment 
is  due  to  the  late  Professor  John  Craig,  and  to  Dr.  II.  J.  Webber 
and  Dr.  H.  H.  Love.  Facilities  for  work  were  furnished  by  the  depart- 
ments of  Horticulture  and  Plant  Breeding  of  the  New  York  State 
College  of  Agriculture. 


GENETIC   LITERATURE    RELATING    TO   MATTHIOLA 

The  work  of  Correns  (1900)  on  Matthiola  furnished  one  of  the 
earliest  confirmations  of  Mendel's  law,  and  also  pointed  to  complica- 
tions not  found  by  Mendel.  The  earlier  literature,  according  to  Correns, 
gives  no  indication  of  the  study  of  Matthiola  hybrids  beyond  the  first 
generation. 

In  his  later  paper  on  aberrant  hybrid  ratios,  the  same  author 
(1902)  discusses  complications  in  maize  and  in  Matthiola.  After 
referring  the  deviations  found  in  maize  to  selective  pollination,  he 
considers  a  suggestion  of  de  Vries  relating  to  environmental  modi- 
fication of  Mendelian  ratios,  and  himself  suggests  the  possibility  of 
selective  elimination  of  gametes.  He  says  (pp.  171-172),  "Solche 
Einfliisse  brauchten  nicht  alle  Sorten  Keimzellen  des  Bastardes  gleich- 
massig  zu  treffen,  sondern  sie  konnten  eine  Sorte  starker  angreifen  als 
die  andere." 

Von  Tschermak  (1904,  1912)  has  made  extensive  studies  of 
Matthiola  hybrids,  considering  mainly,  as  did  Correns,  pubescence  and 
flower  color.  The  latter  of  these  papers  on  hybrids  in  the  genera 
Matthiola,  Pisum,  and  Phascolus  represents  a  careful  analytical  test 
of  the  "factor  hypothesis"  of  segregating  inheritance,  leading  to  the 
conclusion  that  the  applicability  of  this  hypothesis  is  strongly  con- 


J 


1919]  Frost:    Mutation   in  Matthiola  80 

firmed  by  the  results  secured.  This  work,  with  that  of  Miss  Saunders, 
leaves  no  possibility  of  doubt  that  the  typical  Mendelian  mechanism  is 
present  in  Matthiola. 

The  most  extensive  genetic  work  on  Matthiola  is  evidently  thai  <>f 
Miss  Saunders,  reported  by  herself  (1911,  1911a,  1913,  1913a,  1915, 
1916)  and  by  Bateson  and  Saunders,  with  others  (1902,  1905,  1906, 
1908).  This  also  is  work  on  heredity  in  hybrids,  with  special  emphasis 
on  the  factorial  interpretation  of  the  various  complications  relating 
to  pubescence  and  to  "doubleness"  of  flowers. 

Goldschmidt  (1913)  has  explained  the  inheritance  of  doubleness 
by  sex  linkage  and  lethal  action  of  a  femaleness  factor  in  pollen 
formation,  and  his  interpretation  has  been  criticized  by  Miss  Saunders 
(1913).  I  (Frost,  1915)  have  presented  a  somewhat  different  lethal- 
factor  scheme,  and  Miss  Saunders  (1916)  has  since  restated  her  views 
and  criticized  mine. 

Muller  (1917)  has  cited  the  inheritance  of  doubleness  as  a  case  of 
"balanced  factors,"  in  apparent  agreement  with  my  formulation. 

Apparently  no  one  but  the  present  writer  (Frost,  1912,  1916;  see 
also  review  by  Bartlett,  1917)  has  reported  experimental  evidence  of 
any  notable  tendency  to  apparent  mutation  in  the  genus,  although 
de  Vries  (1906,  p.  338)  mentions  the  occasional  occurrence  of  vigorous, 
rigidly  upright  individuals  (a  gigas  type?),  known  at  Erfurt  as 
"generals,"  and  refers  to  the  rare  mutative  occurrence  of  single 
flowers  on  branches  of  double-flowering  plants.  Doubleness,  and  color 
variations  in  considerable  number,  have  evidently  arisen  under  culti- 
vation, probably  through  mutative  changes. 


METHODS 

The  general  cultural  methods  employed  for  the  first  three  genera- 
tions have  been  very  briefly  described  elsewhere  (Frost,  1911). 

The  plants  of  the  first  four  years  were  grown  in  pots  in  the  green- 
house. The  plants  of  the  first  generation  came  from  one  or  both  of 
two  packets  of  commercial  seed  planted  in  the  fall  of  1906.  and  all 
plants  in  the  later  cultures  (possibly  excepting  series  18)  were 
descendants  of  these.  The  cultures  will  in  general  be  designated  by 
the  year  in  which  the  seed  was  sown ;  the  field  and  greenhouse  cultures 
of  1911  are  indicated  by  1911F  and  1911 H  respectively. 

Part  of  the  seed  planted,  especially  in  1908,  came  from  unguarded 
flowers.     The  seed  lots  where  this  occurred  will  be  indicated  in  the 


86  University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 

tabulation  of  parental  data  by  italic  figures,  while  protection  possibly 
defective  will  be  indicated  by  an  asterisk.  It  is  not  probable  that 
much  vicinism  occurred  in  the  greenhouse  cultures,  since  this  plant 
is  well  adapted  to  self  fertilization. 

In  the  first  year's  (1906)  cultures  the  plants  in  each  experimental 
environment  were  separately  numbered.  Each  plant  was  designated 
by  its  number  preceded  by  two  letters  indicative  of  the  environment. 
For  greenhouse  temperature  these  letters  were  C  (cool),  M  (medium 
temperature),  and  W  (warm)  ;  for  potting  soil"'  they  were  S  (sand), 
L  (unfertilized  "loam"),  and  G  ("good"  soil,  fertilized).  Thus  CS1 
CS2,  WG9,  etc.,  were  pedigree  numbers  of  the  first  generation,  and 
CG2-M8  and  WG9-C10  of  the  second  generation.  A  few  syncotyle- 
donous  plants  outside  the  regular  cultures  of  1907  were  called  WG9- 
synl,  etc. 

For  the  work  at  Riverside  a  new  system  of  numbering  was  adopted, 
better  suited  to  ordinary  pedigree  cultures,  and  the  numbers  from 
this  system  are  used  below  in  the  individual  treatment  of  all  but  one 
of  the  mutant  types  ("early").  This  is  essentially  Webber's  (1906, 
p.  308)  system,  except  that  each  initial  or  P,  individual  of  a  series  is 
indicated  by  a  letter;  a  full  description  has  beeu  published  (Frost, 
1917).  With  Matthiola  each  type  or  cross  between  two  types  that  is 
tested  receives  a  series  number,  the  apparent  mutants  themselves 
always  being  taken  as  the  initial  individuals  of  their  selfed  series. 

The  cultures  of  1908  included  progeny  of  various  parents,  one  being 
WG9-C10,  an  early  and  few-noded  plant  suspected  of  being  a  mutant. 

The  cultures  of  1910  consisted  of  a  second-generation  test  of  WG9- 
C10,  and  a  first-generation  test  of  other  possible  mutants,  with  control 
lots.  The  plants  were  all  grown  on  one  bench  in  one  greenhouse 
(house  C),  from  thirty  lots  of  fifteen  seeds  each,  lots  1-17  relating  to 
WG9-C10.  The  parents  descended  from  WG9-C10  (see  table  7)  were 
selected  as  those  with  fewest  internodes,  a  medium  number  of  inter- 
nodes,  and  most"  internodes  in  each  house  of  the  1908  cultures,  earli- 
ness  of  fiowering  being  considered  when  parents  were  alike  in  number 
of  internodes.  The  control  parents  were  both  few-noded  and  many- 
nocled,  relatively  to  their  sibs. 

In  1911  eighty  progeny  lots  were  grown  in  the  field  at  Ithaca. 
Lots  1  to  28,  transplanted  from  the  greenhouse,  paralleled  the  test  of 


■j  Soil  experimentally  varied  only  in  the  1906  cultures,  temperature  varied  in 
the  two  following  years  also. 

«  For  house  M,  not  the  highest,  which  wras  exceptionally  high,  but  the  next 
to  the  highest. 


1939  /  i-o.i1  •    Mutation  in  Matthiola  87 

WG9-C10made  in  1910-11 ;  all  available  progeny  of  WG9  CIO,  excepl 
the  erenate-leaved  apparenl  mutanl  WG9-C10-C10,  were  tested,  with 
check  lots  between  as  before.  Soil  differences  and  unavoidable  differ- 
ences between  lots  in  time  of  transplanting  combined  with  hot  weather 
and  drought  to  reduce  the  value  of  the  results.  The  remaining  fifty- 
two  lots,  all  field-sown,  included  a  further  lest  of  the  heredity  of 
aberrant  types  other  than  early.  .Most  of  these  lots,  however,  were 
progeny  of  Snowtlake  parents,  grown  to  obtain  evidence  on  the  relation 
of  temperature  to  mutation  and  on  the  inheritance  of  douhleness  of 
flowers,  and  therefore  the  results  are  not  reported  here. 

The  191111  cultures  constituted  a  coldframe  and  greenhouse  prog- 
eny test  of  mutant  types,  mainly  in  the  second  generation,  the  plants 
being  grown  in  flats. 

There  was  added  in  1912-13  a  small  greenhouse  test  bearing  on  the 
supposed  mutative  origin  of  WG9-C10,  in  view  of  the  apparent  possi- 
bility that  AVS1  or  "WL10,  in  the  same  house  with  the  unbagged  WG9. 
might  have  been  heterozygous  for  the  early  type — cross  pollination 
then  giving  the  apparent  mutant. 

Further  progeny  tests  of  the  mutant  types  have  been  made  in  the 
field  at  Riverside,  beginning  in  the  fall  of  1913.  Mainly  on  account 
of  the  unsuitability  of  the  usually  hot  and  dry  climate  of  River- 
side, the  cultures  have  been  largely  experimental  and  always  on  a 
small  scale,  and  germination  or  development  has  sometimes  been  un- 
satisfactory. Cultures  have  been  started  in  October.  November. 
January,  and  February,  and  a  trial  culture  in  progress  at  the  time 
of  writing  was  started  in  August.  Some  of  the  plants  of  the  1915-16 
cultures  were  kept  until  the  summer  of  1917,  and  many  of  them 
flowered  for  the  first  time  when  about  a  year  old. 

In  the  cultures  of  1913,  growth  was  largely  unsatisfactory,  and 
with  part  of  the  plants  aphid  injury  interfered  more  or  less  with  the 
classification  of  types.  In  the  cultures  of  1914,  the  seeds  were  largely 
lost  through  toxic  effects  favored  by  very  shallow  planting  (as  at 
Ithaca)  and  strong  evaporation  from  the  soil.  In  subsequent  planting, 
the  seeds,  planted  singly  in  small  paper  pots,  were  dropped  into 
relatively  deep  holes  punched  in  the  soil,  and  covered  with  sand. 

The  only  field-grown  plants  closely  resembling  those  grown  in  the 
greenhouse  at  Ithaca,  it  may  be  noted,  have  been  those  of  the  1917 
cultures,  grown  in  a  lathhouse  with  added  shade  from  muslin. 

In  the  cultures  of  1915-16,  with  partial  shade  and  more  frequent 
irrigation  than  before,  development  was  in  general  good ;  but  even 


88 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


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L919]  Frost:   Mutation  in  Matthiola  89 

here  the  mutant  typos,  with  one  exception,  often  failed  to  grow  satis- 
factorily or  to  set  seed.  Iii  feci  ion,  probably  by  Fusarium,  evidently 
was  the  cause  of  the  death  of  many  of  these  plants  in  their  second 
season. 

With  all  cultures  grown  after  (probably)  those  of  1906,  special 
care  was  taken  to  secure  random  samples  of  seed,  and  after  1908  no 
plants  were  rejected.  The  only  exception  to  this  statement  is  the 
rejection  of  one  pot  out  of  every  fifteen,  by  number  and  systematically, 
in  the  first  twenty  progeny  lots  of  1910.  For  the  earlier  cultures,  a 
certain  amount  of  selection  must  be  recorded,  as  follows.  In  1906 
the  small  and  the  largest  plants  were  omitted  at  potting,  and  probably 
any  weak  and  abnormal  seedlings  had  been  omitted  at  the  preceding 
transplanting.  In  1907  all  markedly  weak,  late,  or  abnormal  seedlings, 
as  determined  mainly  by  the  appearance  of  the  cotyledons,  were 
omitted  at  the  first  transplanting;  and  the  same  was  done  in  1908, 
except  that  certain  lots  from  old  seed  were  unselected.7 

These  last  lots  were  arranged  at  transplanting  in  such  a  way  that 
the  weak  and  abnormal  plants  came  at  the  end  in  each  lot. 


EXPERIMENTAL  DATA 

The  Occurrence  op  Apparent  Mutants 

In  the  cultures  of  1906,  88  plants  were  grown  to  maturity,  none 
of  these  being  suspected  of  mutation.  In  the  cultures  of  1907,  among 
170  plants  one  striking  variant  appeared;  this  plant,  WG9-C10,  was 
exceptionally  small  and  early  in  blooming. 

In  the  cultures  of  1908,  714  plants  were  available,  including  ap- 
parent mutants  in  several  hereditary  lines  as  indicated  in  table  1.  A 
striking  feature  of  the  results  is  the  scarcity  of  apparent  mutants 
among  the  seedlings  classed  as  strictly  normal  at  transplanting;  prob- 
ably the  scarcity  in  the  preceding  years  was  due  mainly  to  the  rejection 
of  abnormal  seedlings  (see  "Methods").  The  first,  second,  and  fourth 
of  these  forms  have  been  common  in  later  cultures,  while  the  third 
and  fifth  have  been  rarer;  the  last  three,  if  seen  at  all  elsewhere,  have 
not  being  recognized  as  belonging  to  the  same  types  as  these  three 
plants. 


One  tiny  plant  from  WG9,  probably  not  viable,  was  discarded. 


90 


University  of  California  Publications  in  Agricultural  Sciences       \  Vol.  4 


Table  2  shows  the  numbers  and  percentages  of  apparent  mutants 
found  in  the  cultures  of  1910  and  1911P.  Since  the  early  type  seems 
to  differ  from  Snowflake  only  in  size  and  earliness,  and  is  probably 
inherited  without  special  complications,  the  available  progeny  of  early- 
type  parents  are  included  in  the  totals.  The  progeny  of  all  parents 
recognized  as  belonging  to  other  aberrant  types  are  omitted.  The 
second  column  under  "Percentage  of  mutants"  omits  doubtful  types 
and  individuals,  but  includes  some  individuals  for  which  some  doubt 
was  indicated  in  the  original  records.     One  rare  type  of  1911,  large- 


Table  2 
Aberrant  types:  occurrence  among  progeny  of  Snowflake  and  early  parents. 
Apparent  selective  elimination  at  or  after  germination  in 
field-sown  cultures." 


Cultures 


Greenhouse,  1910 

Field,  1911,  seed 
house-sown 

All  above 

Same, Snowflake  par- 
ents only 

Field,1911,seed  field- 
sown  (parents  all 
Snowflake  ) 


Progeny  examined'1 


338 

2072 
2410 

1304 


3927 


Percentage  of  apparent  mutants 


All  counted 


5.03  ±  .82<: 

5.31  ±  .33 
5.27  ±  .31 


4.3c 


.41 


2.34  ±  .24 


Doubtful  omitted 


4.14 

4.63 

4.56 


.77 

.31 
.29 


3.74  ±  .38 


1.55 


.22 


0  Germination  in  greenhouse-sown  lots,  counting  only  plants  examined  for 
type,  93.2  per  cent;  in  field-sown  lots,  45.1  per  cent. 

b  Including  some  plants  of  uncertain  type,  indicated  for  some  lots  (when 
apparently  not  Snowflake)  in  tables  1  and  3. 

c  For  the  calculation  of  these  probable  errors  the  percentages  on  the  third 
line  are  used  as  p. 

leaved,  here  omitted,  has  proved  to  be  genetic,  but  its  determination 
in  these  cultures  was  in  general  uncertain.  A  stricter  criterion  for 
the  second  column,  elimination  of  all  individuals  not  considered  posi- 
tively determined,  was  used  in  the  calculations  for,  the  tables  for  the 
inheritance  of  the  separate  mutant  types. 

Evidently  the  more  rigorous  field  conditions  of  1911  eliminated 
many  of  the  "mutants"  at  or  soon  after  germination.  The  "coefficient 
of  mutability"  with  good  germination,  as  was  the  case  with  the  un- 
selected  cultures  of  1908,  seems  to  be  near  5  per  cent,  a  surprisingly 
high  figure  if  immediate  true  mutation  is  responsible. 

Before  the  aberrant  types  are  considered  separately,  we  may 
examine  (table  3)  a  detailed  illustration  of  their  occurrence  in  larger 
cultures.  It  seems  probable,  from  this  evidence,  that  any  descendant 
of  WG9  was  capable  of  producing  any  of  the  mutant  types  so  far 


19191 


Frost :    Mutation  in    Mai 


91 


2  <* 


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a  - 

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g  ■ 


tOtOtOtOtOtO—  —  —  —  —  —  —  —  tO  tO  IO  —  — 

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re:      —  :      :      —  —  : 


Field  lot 


Generation  i 


Generation  2 


Generation  3 


Total    progi  nj     ol 
detei  minable    I  j  i" 


Smooth-leaved 


Small-smooth- 
er, ed 


Crenate-leavcd 


Semi-crenate- 
leaved 


Pointed-crenate- 

leaved 


—  to  i—  :  p— ':     to  —  —  :      — :      —  —  :  —  : 


CO  —  :       tO 


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leaved 


S 1 1  •  1 1 1 1 1  ■  i 


Small-convex- 
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(  'otnpar-t 


Curly-leaved 


Pointed-light- 
leaved 


Large-leaved 


Medium-large- 
leaved 


Large-thick- 
leaved 


Small  stout- 
capsuled 


Jagged-leaved 


All  counted 


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omitted 


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92 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


discovered ;  the  occurrence  of  the  various  types  suggests  a  random 
distribution  among  the  progeny  lots.  This  conclusion  is  confirmed, 
and  extended  to  CG2,  by  the  field-sown  lots  of  1911. 

Various  parents  belonging  to  mutant  types  have  given  other 
mutant  types  among  their  progeny.  There  is  some  reason,  as  table  4 
indicates,  to  suppose  that  parents  of  the  early  type  have  a  more 
marked  tendency  to  produce  these  other  types  than  have  Snowflake 
parents.8 

Table  4 

1910  and  1911F ;  sown  in  greenhouse.     Apparent  mutants  among  descendants 

of  WG9-C10  and  other  ancestors,  comparing  early  parents  (pure  or 

heterozygous)  with  Snowflake  parents. 


Type  of  parent 

Progeny 

Ancestry 

Total 
examined 

Percentage  of  mutants 

All  counted 

Doubtful  omitted 

WG9-C10 

Pure  Snowflake 

Both 

Both 

1  Early 

(  Snowflake 
Snowflake 
Snowflake 
Both 

1046 

558 

806 

1364 

2410 

6.50  ±  .47" 

4 . 30  ±   .64 
4.34  ±   .53 
4.33  ±   .41 

5.27  ±   .31 

5.64  ±   .44 

3.41  ±   .60 
3.97  ±  .50 

3.74  ±  .38 
4.56  ±   .29 

*  For  the  calculation  of  these  probable  errors  the  percentages  on  the  last  line 
are  used  as  p. 


Characteristics  and  Heredity  op  Mutant  Types 

1.  THE  EARLY  TYPE 

So  far  as  is  known,  WG9-C10  (figs.  1,  2)  was  the  only  apparent 
mutant  of  the  early  type  in  the  cultures.  Since,  however,  this 
type  visibly  differs  from  Snowflake  only  or  mainly  in  quantitative 
characters,  it  cannot  be  positively  identified  without  comparative 
progeny  tests,  and  therefore  may  have  been  represented  by  mutant 
individuals  not  used  as  parents.  WG9-C10  was  much  smaller  pro- 
portionately than  were  its  progeny ;  this  difference  was  probably  due 
to  an  embryonic  abnormality,  early  blind  termination  of  the  main 
axis,  which  was  occasionally  observed  elsewhere  and  probably  occurred 
in  this  case.  Plants  of  this  type,  as  compared  with  Snowflake,  are,  in 
general,  fevver-noded,  smaller,  and  earlier  in  blooming. 

The  principal  data  from  the  cultures  of  1908  are  shown  in  tables 
5  and  6,  which  also  indicate  the  later  conclusions  as  to  the  segregation 
of  the  early  type  in  the  cultures  of  this  year ;  figures  3  and  4  illustrate 


8  Inspection  of  the  data  in  detail  indicates  that  this  difference  is  not  due  to 
the  possible  tendency  in  parents  grown  in  the  warm  house  to  more  frequent 
apparent  mutation. 


1919] 


Frost:   Mutation  in  Mattliiola 


93 


Table  5 
Cultures  of  1908.    Time  from  sowing  to  emergence  of  corolla  of  earliest  flower 
of  ■primary  cluster.     Frequency  distributions.' 


Singles 

Doubles 

House  C 

House  M 

House  W 

House  C 

House  M 

House  \V 

Parents: 

WG9- 

WG9- 

WG9- 

WG9- 

\\i  ,'i 

WG9- 

C10 

Rest 

C10 

Res 

'         CIO 

Res 

1        CIO 

Rest 

CIO 

Rest 

C10 

Rest 

D.I  7-  h 

110 

It 

111 

U 

112 

113 

111 

115 

116 

1 

1 

117 

"it 

118 

it 

2 

119 

3 

120 

"it 

4 

121 

it 

2 

1 

1 

122 

3 

2 

123 

8 

It 

i 

1 

2 

124 

i 

4 

1 

2 

125 

7 

it 

5 

1 

3 

126 

16 

7 

7 

127 

3 

it 

2 

9 

2 

128 

4 

3 

\    z 

8 

5 

129 

7 

it 

4 

8 

7 

130 

1 

it 

3 

12t 

4 

131 

i 

2 

4 

2 

12 

3 

132 

"lj 

1 

2 

7 

8 

133 

m 

1 

i 

4 

7 

134 

i 

2 

2 

1 

2 

7 

135 

4 

4 

4 

6 

6 

136 

1 

i 

1 

3 

1 

4 

137 

7 

2 

3 

3 

i 

2 

138 

10 

1 

9 

4 

l 

1 

139 

18t 

1 

i 

2 

8 

l 

3 

140 

i 

7 

1 

r     .... 

4 

13 

3 

141 

10 

1 

"l 

9 

i 

3 

142 

4 

6 

15 

l 

1 

143 

4 

i 

5 

"2 

10 

2 

144 

4 

2 

9 

2 

145 

3 

6 

3 

146 

i 

5 

2 

147 

4 

148 

2 

1 

1 

149 

2 

1 

150 

r 

1 

2 

151 

1 

1 

r 

152 

2 

153 

1 

i 

154 

155 

1 

1 

l 

■  Daggers  (t)  indicate  the  position  and  number  of  apparent  mutants.  Double 
daggers  (t)  indicate  inheritance  of  parental  type  (here,  early);  all  single  progeny 
of  WG9-C10  here  reported  have  been  tested  for  inheritance  of  this  type.  The 
conventional  statistical  constants  corresponding  to  the  house  totals  of  tables  5 
and  6  have  been  published  (Frost,  1911);  the  means  for  flowering  given  there 
are  too  high  by  one  half-day. 

b  To  time  of  observation  (upper  limit  of  one-day  class). 


94 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


Table  5.    Cultures  op  1908  (Continued) 


Singles 

Doubles 

House  C 

House  M 

House  W 

House  C 

House  M 

House  VV 

Parents: 

WG9- 
C10 

Rest 

WG9- 
CIO 

Rest 

WG9- 
C10 

Rest 

WG9- 
C10 

Rest 

WG9- 
C10 

Rest 

WG9- 
C10 

Rest 

Days  b 

156 
157 
158 
159 
160 
161 
162 
163 
164 
165 
166 
167 
168 
169 
170 
171 
172 
173 

1 

1- 

1 

it 

"  Daggers  (f)  indicate  the  position  and  number  of  apparent  mutants.  Double 
daggers  (t)  indicate  inheritance  of  parental  type  (here,  early);  all  single  progeny 
of  WG9-C10  here  reported  have  been  tested  for  inheritance  of  this  type.  The 
conventional  statistical  constants  corresponding  to  the  house  totals  of  tables  5 
ami  (5  have  been  published  (Frost,  1911);  the  means  for  flowering  given  there 
are  too  high  by  one  half-day. 

b  To  time  of  observation  (upper  limit  of  one-day  class). 

the  difference  in  earliness  between  the  early  and  SnowHake  types.  The 
parents  grouped  under  "rest"  include  CGl2  and  WG9  themselves,  with 
four  progeny  of  the  former  and  eight  of  the  latter.  Of  these  fourteen 
parents,  not  one  has  produced  exceptionally  few-noded  progeny  like 
those  of  WG9-C10. 

Apparently  WG9-C10  was  heterozygous  for  a  "few-nodedness" 
factor  not  carried  by  any  of  the  other  parents  tested.  Neither  in 
the  1907  cultures  nor  in  the  1908  cultures  now  under  consideration 
did  the  data  suggest  that  WG9  itself  was  similarly  heterozygous. 
Tables  5  and  6  include  the  first  30  progeny  of  WG9,  for  each  house, 
as  arranged  at  the  first  transplanting,"  88  plants  altogether;  including 
the  remaining  plants,  mainly  weak  or  abnormal  at  transplanting,  the 
total  is  116.  One  of  the  F2  plants  (WG9-syn3-M10)  was  very  sug- 
gestive of  the  early  type,  but  (tables  12  and  13)  it  gave  only  Snow- 
flake  progeny  in  a  small  test. 


*  See  page  89.     Two  plants  not  producing  a  normal  main  inflorescence   are 
omitted. 


L9191 


Frost:    Mutation  in  MniilmtUi 


95 


Tabu    6 

!    n-stem  internodes  below  first  flower-bearing 

until .    i'n  qu<  ncy  disti  b 


Singles 

1 1  lubles 

House  C 

House  M 

H 

mse  W 

House  ' ' 

House  M 

House    W 

Parents: 

WG9 

CIO 

Real 

WG9 
CIO 

Res 

1       Cl( 

*"     Rest 

WG9 

cm 

Res 

t      WG9 
CIO 

Rest 

WG9 
CIO 

' 

Internodes 

16 

U 

17 

18 

19 

Tit 

20 

it 

i 

21 

2« 

22 

n 

"l 

1 

23 

1 

24 

9 

25 

i 

2f 

1  + 

1 

"2 

25 

26 

29 

i" 

27 

i 

"i 

1 

1 

22 

2t 

28 

17 

6 

9 

i 

29 

24 

1 

14 

30 

13 

1 

i 

2 

22 

1 

31 

8 

2 

27 

32 

2 

7 

5 

33 

1 

15 

1 

t 

3 

34 

16 

4 

1 

35 

2 

19 

1 

t    z 

5 

36 

4 

1 

t    .... 

i 

6 

37 

1 

1 

t    .... 

8 

38 

8 

5 

39 

3 

13 

40 

1 

6 

41 

1 

r 

8 

42 

it 

1 

+ 
+ 

6 

43 

It 

12 

44 

9 

45 

i 

t    z 

6 

46 

4 

3 

47 

3 

3 

48 

4 

49 

1 

3 

i' 

50 

6 

51 

1 

3 

2f 

52 

10 

1 

53 

6 

54 

2 

2 

55 

1 

3 

56 

7 

i 

57 

8 

58 

1 

59 

1 

r 

60 

3 

61 

62 

1 

a  See  note  a  to  table  •"">. 


96  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

The  differentiation  of  the  early  race  is  very  marked ;  with  the 
singles,  in  fact,  the  later  cultures  indicate  no  case  of  overlapping  in 
the  1908  cultures,  in  either  character,  between  extracted  pure  Snow- 
flake  and  pure  or  heterozygous  early.  The  total  sterility  of  the  doubles 
necessarily  leaves  their  constitution  somewhat  in  doubt. 

The  cultures  of  1908  so  far  suggest  that  "WG9-C10  was  a  mutant. 
To  be  reasonably  certain,  however,  we  must  have  further  evidence 
(1)  on  the  fact  and  mode  of  inheritance  of  the  supposed  new  type, 
and  (2)  on  the  possibility  that  either  WG9  or  some  other  plant  of 
the  cultures  of  1906  brought  the  character  into  the  cultures.  "We  shall 
now  consider  somewhat  extensive  evidence  bearing  on  these  points, 
concluding  with  a  special  test  of  the  possibility  of  vicinism. 

"When  I  last  saw  the  warm-house  plants  of  1906,  three  were  known 
to  be  singles,  and  all  but  two  of  the  rest  were  recorded  as  certainly 
or  probably  doubles.  Seed  was  secured  from  these  three  singles  only, 
and  presumably  no  other  singles  occurred  in  the  house.  Since  this 
seed  was  all  from  unguarded  flowers,  we  must  consider  the  possibility 
that  WTS1  or  "WL10,  the  other  warm-house  singles,  brought  the  early 
factor  into  the  cultures.  It  is  also  barely  possible  that  pollen  was 
brought  to  WG9  from  some  plant  not  in  this  greenhouse. 

These  two  parents  were  tested  in  supplementary  cultures,  in  house 
C  in  1907,  and  in  house  W  in  1908.  The  1907  progeny  averaged 
slightly  earlier  than  those  of  other  parents,  but  this  may  have  been 
due  to  their  position,  which  was  much  nearer  a  partition  separating 
the  house10  from  a  warm  greenhouse.  Unfortunately  the  internodes 
were  not  recorded. 

In  the  1908  cultures  these  lots  were  potted  two  days  later  than 
most  of  the  other  lots  and  one  day  later  than  the  "WG9  lot,  and  for 
some  unknown  reason  the  "WL10  lot  wilted  badly  for  some  days.  The 
parents  in  question  gave  singles  (16  and  11  plants  respectively)  which 
when  compared  with  progeny  of  CG2  and  "WG9  (23  and  15)  might 
suggest  that  the  parents  were  heterozygous  for  the  early  type.  The 
results  with  the  similar  numbers  of  doubles  decidedly  disagree  with 
these,  and  suggest  that  cultural  accidents  produced  the  differences ; 
the  "WS1  lot  was  not  exceptional,  while  all  the  "WL10  progeny  were 
grouped  near  the  lower  end  of  the  range  of  the  other  lots.  In  view  of 
all  the  facts,  the  data  hardly  deserve  tabular  presentation,  but  they 
raise  a  question  requiring  further  study;  a  later  test  is  reported  below. 


4) 


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Frost:   Mulnl'mn  in  Matthiola 


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University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


In  the  cultures  of  1910  and  1911F,  all  the  1908  progeny  of  WG9- 
C10  were  tested.  On  account  of  the  variable  nature  of  the  quanti- 
tative character  involved,  an  elaborate  study  was  necessary.  Only 
small  cultures  could  be  grown  in  the  greenhouse ;  these  were  supple- 
mented by  larger  lots  in  the  field  in  1911,  but  inhibition  of  flowering 
by  the  hot  summer,  together  with  the  effects  of  disease  and  soil  varia- 
tions, made  the  field  results  erratic  and  necessitated  special  methods 
of  treatment  of  the  evidence. 


Singles 
Doubles 


• 

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• :____; ___-_; — ^— 

_____ _________________ _£__Z__1___- 

____* _____ ______ 


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WG9 

Ancestry 


Chart  1.  Cultures  of  1910.  Internodes:  parental  values  and  progeny  means 
(respectively  shown  by  dots  and  lines)  for  progeny  lots  1  to  17,  omitting 
aberrant  progeny.    Parental  values  should  be  compared  only  for  the  same  house. 


Table  7  gives  the  available  data  for  the  parents  of  the  1910  cultures, 
and  the  numbers  of  progeny  available  for  quantitative  data.  The 
order  of  the  pedigree  numbers  here  is  the  same  as  that  of  the  progeny 
lots  on  the  greenhouse  bench.  For  convenience,  the  1910  tests  of  other 
mutant  types,  together  with  tests  of  several  Snowflake  parents,  are 
included  in  the  table  (lots  18  to  30). 


1919]  Frost:    Muta  Matthiola  99 

The  plants  were  grown  in  house  C  of  the  previous  work.    Two  or 
three  plants     one  shown   in   li'_r.  25)    were  extremelj    vigorous,   pre 
sumahly  because  of  some  accidental  soil  difference;  aside  from  these, 
a   few   apparenl   mutants,  and  a   few  plants  otherwise  abnormal,  the 
plants  were   fairly   uniform   excepl    where   heterozygosis   was   to   be 

expected. 

The  data  for  time  of  flowering,  as  with  the  1908  cultures,  show  the 

same  main  features  as  the  internode  data,  and  only  the  latter  will  be 
considered  in  detail.  The  types  were  again  more  widely  different  in 
internodes  than  in  earliness,  a  fad  which  seems  to  indicate  that  the 
early  type  grows  more  slowly  than  Knowllake. 

So  large  and  so  regular  are  the  differences  in  internodes  that  the 
means  of  these  very  small  lots  seem  worthy  of  present  at  ion  (chart  1 )." 
Apparently  the  I'ew-noded  character  was  carried,  among  the  nine 
parents  descended  from  VYG9  ('10.  by  all  except  the  three  parents 
having  the  highest  cumbers  in  their  respective  houses. 

Tables  8  and  9  give  the  internode  frequencies  for  the  singles  and 
doubles  respectively,  by  separate  progeny  lots  and  by  groups  of  similar 
ancestry.  The  range  of  variation  for  the  cheek  lots,  omitting  the 
indicated  apparent  mutants  and  other  apparently  abnormal  plants,  is 
rather  surprisingly  small,  as  is  the  case  with  the  cool-house  cultures 
of  1908.  The  three  late  progeny  of  WG9-C10  give  lots  closely  corre- 
sponding in  range  to  the  check  lots,  only  one  individual  falling  below 
the  range  of  the  combined  check  lots.  The  six  early  and  medium 
progeny  of  WG9-C10,  on  the  other  hand,  give  distributions  of  far 
greater  range  than  do  the  check  parents,  extending  to  much  lower 
values. 

Tables  10  and  11  give  the  ordinary  statistical  constants  for  the 
grouped  lots.  The  mean  number  of  internodes,  for  both  singles  and 
doubles,  is  about  25  per  cent  lower  in  the  progeny  of  the  six  I'ew- 
noded  parents,  the  difference  being  not  far  from  ten  times  as  great  as 
its  probable  error.  The  increase  in  variability  with  the  progeny  of 
the  early  parents  is  also  striking,  and  the  difference  is  about  five  to  six 
times  its  probable  error.  With  time  to  flowering,  it  may  be  noted,  the 
differences  are  similar  to  those  with  internodes,  but  somewhat  less 
marked  in  the  case  of  the  mean ;  the  flowering  data  are  not  given  here. 

It  is  plain  that  the  previous  conclusion  as  to  the  heterozygous  nature 
of  WG9-C10  is  sustained.     The  elimination  of  the  apparent  mutants 


ii  Calculated  with  the  apparent  mutants  and  four  other  apparently  abnormal 
plants  eliminated;  see  tables  8  and  0. 


100 


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1919]  Frost:   Mutation  fa  Matthiola  105 

;hh1  the  other  abnormal  plants  presumably  gives  a  better  comparison 
as  to  mean  and  variability,  but  the  conclusion  is  the  same  in  either 
case.     The  three  many-noded   (late)   parents  descended   from  WG9- 

('10  give  no  definite  indication  of  being  genetically  different  from  the 
"check"  lots  not  descended  from  W<i9-C10,  while  the  variability  con- 
stants are  sufficient,  taken  alone,  to  make  probable  the  genetic  differ- 
entiation of  the  Eewer-noded  progenj  of  WG9-C10.  Apparently  all 
the  fewer-noded  progeny  of  "WG9-C10  thai  were  tested — seven,  when 
YY  (I9-C10-C10,  a  crenate-leaved  apparent  mutant  (tables  12  and  13), 
is  included — were  either  simplex  or  duplex  for  presence  of  an  earliness 
factor  or  factors. 

The  variability  of  all  the  thirty  progeny  lots,  taken  together,  is 
high,  as  might  be  expected,  though  decidedly  below  that  of  the  progeny 
of  early  parents.  This  high  variability  is  due  only  in  very  small  part 
to  the  progeny  of  the  five  or  six  supposedly  mutant  parents;  the  last 
thirteen  lots,  alone,  are  much  less  variable  than  the  mixed  early  lots. 
The  portion  of  the  cultures  containing  these  progeny  lots  from 
aberrant  parents  was  conspicuous  for  irregularity  of  germination,  and, 
on  the  whole,  a  relatively  low  rate  of  germination. 

A  few  of  the  last  thirteen  lots  give  more  evidence  bearing  on  the 
origin  of  WG9-C10.  The  early  WG9-syn3-M10  (tables  12  and.  13) 
gives  no  evidence  of  genotypic  differentiation  from  its  ordinary  sib, 
WG9-syn3-Mll  ;  WS1-WJ6,  another  phenotypically  early  parent, 
also  failed  to  transmit  earliness  to  its  progeny.  CG2-C2-C6,  on  the 
other  hand,  although  itself  an  ordinary  plant,  shows  a  rather  sus- 
picious tendency  to  the  production  of  early  and  few-nocled  progeny, 
but  better  evidence  would  be  required  for  any  positive  conclusion. 
WG9-C10-C10  appears,  from  the  data  in  tables  12  and  13  and  from 
observation  of  the  flowering  of  plants  of  the  next  generation  in  the 
1911H  cultures,  to  have  been  heterozygous  for  the  early  type,  as  well 
as  for  the  crenate-leaved  type.  We  find  in  this  test  no  definite  indi- 
cation that  the  early  type  has  appeared  elsewhere  than  in  WG9-C10 
and  its  descendants. 

The  F2  progeny  of  WG9-C1,  an  abnormal  plant  whose  F,  progeny 
were  unusually  and  uniformly  early  but  not  few-noded,  have  been 
included  with  the  other  check  lots  without  question.  This  treatment 
seems  justified  by  the  flowering  data,  which  do  not  indicate  any 
repetition  of  the  precocious  development  of  the  first -generation  plants; 
the  peculiarities  of  the  Fl  cultures,  if  not  a  mere  cultural  accident, 
presumably  depended  on  the  very  abnormal  development  of  the  parent, 


106 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


Table  12 

1910,  greenhouse,  lots  18  to  30.     Number  of  main-stem  internodes  below  first 
flower-bearing  node.     Frequency  distributions  for  singles." 


Gen.  1 

CG2 

WG9 

WSl 

WL10 

Ances-< 

Gen.  2 

C2 

W4 

syn  (M) 

3 

C228 

W2 

CIO 

W2 

W7 

Wo  16 

Wo  25 

W3  20 

try 

Gen.  3 

CG 

W3 

C17 

M10 

Mil 

M7 

CIO 

W2 

C5 

Inter- 

nodes 

21 

1 

It 

22 

It 

23 

It 

24 

1 

25 

26 

1 

It 

2tt 

27 

1 

1 

It 

It 

2 

2 

28 

1 

2 

1 

1 

It 

4 

1 

3 

29 

1 

2 

2 

1 

1 



3 

30 

1 

3 

3 

2 

1 

1 

It 

1 

31 

1 

1 

1 

32 

1 

1 

1 

33 

1 

It 

34 

1 

1 

35 

36 

1 

37 

38 

1 

39 

It 

40 

1 

41 

U 

42 

43 

44 

It 

a  See  table  7  and  notes  to  tables  5  and  8. 


Table  13 
Same  as  table  12,  for  doubles: 


Gen.  1 

CG2 

WG9 

WSl 

WL10 

Ances-^ 

Gen.  2 

C2 

W4 

s 

yn  (M)  3 

Co28 

W2 

cio 

W2 

W7 

Wol6 

Wo  25 

W2  20 

try 

Gen.  3 

C6 

W3 

C17 

M10 

Mil 

M7 

CIO 

W2 

cr» 

Inter- 

nodes 

16 

1 

17 

2 

18 

19 

1 

20 

21 

3 

22 

1 

2 

2 

23 

1 

2 

It 

3tt 

1 

24 

2 

1 

It 

It 

2 

25 

4 

1 

3tt 

2 

It 

It 

1 

1 

1 

26 

2 

2 

2 

1 

1 

2 

It 

27 

2 

1 

2 

2 

3 

3 

1 

2 

28 

1 

1 

1 

2 

5 

1 

29 

2 

1 

1 

2 

30 

3tt 

31 

32 

1 

1 

It 

33 

34 

1 

1 

See  table  7  and  notes  to  tables  5  and  8. 


1919] 


Frost :   Mutation  in  M<rtiln<ii,i 


107 


with  its  aborted  main  ;ixis  ;ui<1  very  late  production  of  a  flowering 

shoot. 

Table  14  shows  the  general  plan  of  the  house-sown  field  cultures 
of  1911.  The  progeny  of  "WG9-C10  were  arranged  as  before  in  the 
order  of  their  numbers  of  internodes  for  each  house  of  the  1908  cul- 
tures, beginning  with  the  lowest  numbers.  The  parental  values  for 
flowering  and  internodes  are  the  values  indicated  by  "  %  "  in  tables  f> 


Table  14 
1911;  field,  plants  transplanted  from  greenhouse.    Ancestry,  seed,  and 

a  a mlii  is  of  progt  uy." 


Lot 

Ancestry 

Seeds 

Number  of 
plants  alive 
■  i'A  days  after 

Numbers  of  plants 
on   mutation   and 

for  data 
lowering 

sown 

Gen.  1 

Gen.  2 

Gen.  3 

sowing 

Total1' 

Singles 

Doubles 

1} 

OS 

/C8 
\C10 

so 

79 

77 

34 

43 

71 

71 

70 

36 

34 

5| 

rC2 

80 

80 

79 

39 

39 

CIO 

C5 

80 

79 

78 

40 

38 

1  C8 

80 

79 

78 

35 

43 

6J 

LCI 

80 

78 

76 

36 

40 

7\ 

C5 

/W18 
\  W24 

80 

79 

77 

37 

40 

8/ 

80 

76 

75 

41 

34 

91 
10 

fM4 

80,26 

77 

76 

30 

45 

M9 

80 

80 

78 

36 

41 

11 
12  f 

CIO 

. 

M6 

80,  63 

77 

77 

34 

42 

M2 

80,7/ 

78 

77 

36 

40 

13 

14  J 

M7 

80 

80 

80 

37 

42 

M8 

80 

74 

70 

33 

37 

WG9 

■ 

15] 

C9 

/C3 

JC7 

80 

78 

78 

30 

48 

16/ 

80 

76 

75 

32 

43 

17] 

W6 

80 

74 

70 

31 

39 

18 

W4 

80,  £1 

70 

65 

26 

38 

19 

Wll 

80 

78 

76 

34 

42 

20 

W9 

80, 19 

76 

72 

24 

47 

21 

• 

CIO 

• 

W5 

80 

79 

75 

33 

42 

22 

W8 

80,  //, 

76 

74 

36 

36 

23 

W7 

80 

75 

72 

32 

40 

24 

W3 

80 

73 

71 

37 

34 

25  J 

W10 

74 

72 

66 

32 

34 

26 

CIO 

80 

60 

59 

27 

32 

27) 
28/ 

C9 

/  W10 

80 

74 

73 

33 

39 

\W24 

80 

80 

78 

32 

45 

"  For  plan  of  arrangement  and  parental  data,  see  page  86  and  tables  5  and  6. 
Seeds  from  unguarded  flowers  are  indicated  by  italic  figures;  where  two  numbers 
are  given  the  first  is  the  total. 

b  Including  twelve  plants  (all  late  mutants)  with  which  determination  of  the 
form  of  flower  was  impossible. 


108 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


and  6,  in  the  order  there  given,  except  that  the  arrangement  by  inter- 
nodes  reverses  the  two-day  difference  in  earliness  of  the  parents  of 
lots  19  and  20;  for  convenient  comparison,  the  parental  and  parent- 
lot  internode  values  are  included  in  table  19. 

Two  progeny  lots  were  set  in  each  of  the  fourteen  rows ;  probably 
the  soil  was  less  favorable  at  the  east  end  of  the  plot,  and  hence  for 
the  even-numbered  lots,  at  least  in  about  the  last  seven  rows  out  of  the 
fourteen. 

The  plants  were  beginning  to  grow  very  rapidly  when  moved  to  the 
field.  On  account  of  deficient  soil  moisture  and  excessive  heat,  the 
transplanting  was  slow  and  in  part  purposely  delayed,  covering  a 
period  of  five  days.    Lots  21  to  28  were  set  three  days  later  than  lots 


80 
70 
60 
00 
40 
30 
20 
10 



ODD 

>. 

fcn 

o 

o 

o 

7Z 

5 



Ph 

1 

2 

3 

4 

5 

6        7        8        9 

10 

11 

12 

13 

14 

(C) 

(C) 

(C) 
Row  number 

(C) 

Chart  2.  1911,  field;  lots  transplanted  from  greenhouse.  Percentages  of 
progeny  lots  not  flowering  by  November  3,  for  singles.  Apparent  mutants  and 
injured  plants  eliminated.  Odd-numbered  lots  represented  by  solid  line.  (C) 
indicate  check  rows.  The  curves  are  broken  between  rows  10  and  11,  where  a 
cultural  difference  enters. 


11  to  20,  and  the  later  loss  of  roots  resulting  seems,  in  spite  of  rain 
coming  the  next  day,  to  have  seriously  delayed  flowering.  Lots  1  and  2 
wilted  badly  after  transplanting,  and  some  difference  in  soil  con- 
ditions in  the  flats,  rather  than  a  genetic  difference,  was  doubtless 
responsible  for  the  exceptional  lateness  of  these  lots.  Lot  20  lost  an 
exceptionally  large  leaf  area  as  a  result  of  transplanting.  A  fungus 
disease  (a  slow  stem  rot)  was  more  common  on  lots  20  to  24  than 
elsewhere ;  it  doubtless  killed  some  young  plants  and  delayed  or  pre- 
vented flowering  in  some  other  cases.  Possibly  the  soil  was  poorer  in 
the  later  rows. 


1919] 


Frost:    Mutation  m  Miittlimhi 


109 


Table  15 
1911,  field;  plants  transplanted  from  greenhouse.    Plants  alive  November  8, 
not  having  flowered.   Singles. 


Non- 

Non-flowering, 

Non-flowering 

Non-flowering, 

How 

Lot 

Hdwim  im- 
plants 

Srii.u  Sake  and 
early  types" 

Lot 

plants 

Snowflake  and 
early  types11 

1 

1 

27 

26 

2 

29 

28  (27) 

2 

3 

5 

2 

4 

7 

5 

3 

5 

9 

9 

6 

11 

11 

4 

7 

7 

5 

8 

17 

17 

5 

9 

0 

0 

10 

2 

2(1) 

6 

11 

1 

0 

12 

9 

7 

•7 

13 

19 

18(17) 

14 

20 

19 

8 

15 

12 

12 

16 

14 

14 

9 

17 

1 

1 

18 

8(7?) 

7(6?) 

10 

19 

0 

0 

20 

3 

3 

11 

21 

8 

8 

22b 

11 

10 

12 

23 

21 

20 

24 

23 

23 

13 

25 

16 

14  (12) 

26 

14 

12 

14 

27 

23 

22 

28 

24 

24 

a  Omitting  non-flowering  apparent  mutants.  For  the  numbers  in  parenthesis, 
"doubtful  mutants"  are  classed  as  mutants.  Two  plants  accidentally  seriously 
injured,  in  lots  14  and  25,  were  counted  out  with  the  mutants. 

b  The  stem-rot  disease  (see  p.  108)  was  evidently  worst  in  lot  22;  some  two  or 
three  of  the  worst  infected  plants  (included  above)  were  nearly  or  quite  dead 
by  November  3. 

Table  16 
Same  as  table  15,  for  doubles. 


Row 

Lot 

Non- 
flowering 
plants 

Non-flowering, 

Snowflake  and 

early  types" 

Lot 

Non-flowering 
plants 

Non-flowering, 

Snowflake  and 

early  types8 

1 

1 

4 

2 

2 

0 

0 

2 
3 

3 

5 

3 

3 

1 
3 

4 
6 

1 

0 

1(0) 
0 

4 

7 

3 

2(1) 

8 

3 

1 

5 

6 

7 

9 
11 
13 

2 
0 
4 

0 
0 

2(1) 

10 

12 
14 

0 
0 

1 

0 
0 

1 

8 

15 

2 

2 

16 

6 

5 

9 
10 
11 
12 
13 

17 
19 
21 
23 
25 

1 

0 
3 
5 

1 

0 
0 
1 
5 

1 

18 
20 
22 

24 
26 

3 
2 

1 
4 
7 

3(2) 

2 

1 

4 

5 

14 

27 

1 

1 

28 

10 

8 

"  See  notes  to  table  15. 


110 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 


Altogether,  these  cultures  are  doubtless  much  less  reliable  for  their 
size  than  the  greenhouse  tests  of  the  early  type,  but  they  nevertheless, 
with  due  consideration  of  the  points  just  mentioned,  seem  to  permit 
of  fairly  safe  conclusions  for  most  of  the  parents. 

The  plants  were  examined  for  flowering  every  other  afternoon  from 
July  4  to  November  3,  inclusive  (73  to  195  days  from  sowing) .  A  very 
large  part  of  the  plants  flowered  in  July,  some  in  August,  and  a  few 
still  later.  Evidently  the  high  summer  temperature  largely  inhibited 
flowering;  many  of  the  singles  and  a  few  of  the  doubles  entirely  failed 
to  flower. 


100 

90 

*>      80 

o 

Ctf 

£      60 

EVE 

V 

1     50 

ODD 

CS 

c      40 
£     30 

— 

20 

10 

1 

2 

3 

4        5 

G        7        8        9 

10 

11 

12 

13 

14 

(C) 

(C) 

(C) 
Row  number 

(C) 

Chart  3.  1911,  field;  lots  transplanted  from  greenhouse.  Percentages  of 
progeny  lots  with  primary  cluster  flowering  or  aborted  by  October  10-16,  for 
singles.     Lines  as  in  chart  2. 

Figures  5  and  6  show  the  plants  in  July.  Growth  was  usually 
vigorous  through  the  season,  but  the  internodes  were  very  short,  the 
branches  numerous,  and  the  region  of  the  terminal  inflorescence  often 
abortive,  so  that  determination  of  the  number  of  main-stem  internodes 
was  not  practicable.  The  emergence  of  the  earliest  corolla  on  the  plant 
was  recorded  at  the  bi-diurnal  observations,  and  at  two  periods  during 
the  season  the  aborted  primary  clusters  were  noted. 

The  data  show  very  definitely  the  transmission  of  "earliness"  by 
the  fewer-noded  progeny  of  WG9-C10.  Tables  15  and  16  show  the 
numbers  of  plants  alive,  without  having  flowered,  on  November  3 ;  the 
figures  are  thus  a  measure  of  lateness.  The  two  progeny  lots  in  each 
row  are  given  one  line  in  each  of  the  tables,  in  order  to  facilitate 
separate  comparison  of  the  fourteen  lots  in  each  end  half  of  the  plot. 


L919] 


Frost :    M  utation  in  M<iitlimi,i 


1 1  1 


The  last  column,  with  the  apparenl  mutants  omitted,  qo  doubl  gives 
the  best  comparison.  The  data  for  the  singles,  reduced  to  percentagi  s 
are  also  given  in  charl  2. 

The  doubles,  w  hich  arc  often  earlier  to  flower  than  the  singles  under 
unfavorable  climatic  conditions,  (lowered  so  generally  thai  table  L6 
presents  no  significant  differences.  The  singles  (table  15),  however, 
give  definite  evidence  of  segregal  ion ;  the  lots  in  rows  2,  5,  6,  and  9  to 
11  all  show  a  tendency  to  early  flowering.     Lot  26,  consisting  of  F1 

Table  17 

1911,  field;  plants  transplanted  from  greenhouse.     Singles  with  primary 
inflorescence  flowering  or  aborted  as  indicated." 


Row- 

Lot 

Aborted  by 
July  29 

Flowering  or 
aborted  by 
Oct.  10-10 

Lot 

Aborted  l>v 
July  29 

Flowering  or 

:il>oi  tcil  l>\ 
Oct.  10-10 

1 

1 

0 

0 

2 

0 

0(2) 

2 
3 

3 
5 

12(13) 

2 

19  (22) 
2 

4 
6 

20 
4 

24  (26) 
8(9) 

4 

7 

2(3) 

3(4) 

8 

1 

1(2) 

5 
6 

7 

9 
11 
13 

22 

25 

1 

27 

29  (30) 
2(4) 

10 

12 
14 

26 
17 

2(3) 

33 
22 

2(3) 

8 

15 

4 

5(6) 

16 

0(1) 

1(2) 

9 
10 
11 
12 
13 

17 
19 
21 
23 
25 

19  (20) 
25  (27) 

4 

2 

0 

20  (23) 
29  (31) 

liiKi 

:?M, 
3(4) 

18 
20 
22 
24 
26 

9 
11 

7 
1 
3 

12 
12 

9 

1(2) 

4(5) 

14 

27 

1 

3(4) 

28 

0 

0(1) 

°  In  this  table  and  also  in  table  18  the  numbers  in   parenthesis  include  the 
probable  but  somewhat  doubtful  cases. 


progeny  of  WG9-C10,  is  decidedly  earlier  than  the  adjacent  lots. 
Lot  25  also  appears  early,  however. 

Tables  17  and  18  give  a  direct  measure  of  earliness,  relating  to  the 
primary  inflorescence  alone.  The  clusters  visibly  aborted  were  in 
general  relatively  far  advanced,  and  those  aborted  at  the  earlier  date 
correspond  to  decidedly  early  flowering;  consequently  the  flowering 
and  aborted  clusters  are  classed  together  as  early.  Chart  3  gives  the 
percentages  for  singles. 

Here  the  data  for  the  doubles  show  fairly  consistent  differences  in 
the  number  aborted  at  the  earlier  date,  while  the  October  totals  are 


112 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


less  regular.  There  are  contrasts  similar  to  those  of  table  15  up  to 
lot  26,  which  is  late,  while  the  check  lots  27  and  28  are  early.  The 
singles  show  the  type  differences  very  strikingly  throughout  lots  1 
to  20,  while  lots  21,  22,  and  26  give  less  positive  indications  of  the 
presence  of  the  early  factor. 

Table  19  gives  the  numbers  of  singles  flowering,  in  primary  in- 
florescence or  elsewhere,  by  November  3,  when  growth  had  practically 
stopped.  The  indications  are  in  general  the  same  as  with  the  data 
already  discussed,  with  better  evidence  than  usual  that  lots  21  and  22 

Table  18 
Same  as  table  17,  for  doubles.* 


Row 

Lot 

Aborted  by 
July  29 

Flowering  or 
aborted  by 
Oct.  10-16 

Lot 

Aborted  by 
July  29 

Flowering  or 
aborted  by 
Oct.  10-16 

1 

1 

15 

30 

2 

6 

22  (23) 

2 
3 

3 

5 

23 
12 

33  (34) 
29  (30) 

4 
6 

21 
16 

35 

30(31) 

4 

7 

17 

30 

8 

8 

22  (24) 

5 
6 

7 

9 
11 
13 

25 

25  (26) 

16 

41 

40  (41) 
28 

10 
12 
14 

24 
23 

22 

41 
40 
31 

8 

15 

27 

37  (39) 

16 

11(12) 

29  (32) 

9 
10 
11 
12 
13 

17 
19 
21 
23 
25 

20 
21 
22 

16  (17) 
17 

35 

41  (42) 

35 

27  (28) 

25 

18 
20 
22 
24 
26 

20  (21) 
21 
18 
10 
9 

32  (33) 
42  (44) 
27  (28) 
16(17) 
15 

14 

27 

21 

29  (30) 

28 

20 

25  (27) 

See  note  to  table  17. 


possessed  the  early  factor.  The  mean  time  of  flowering  is  irregular, 
but  shows  some  effect  of  the  earliness  factor.  Lot  26  is  late  as  to 
number  flowering,  but  early  as  to  mean. 

Table  20,  for  doubles  flowering  by  August  1,  no  doubt  gives  more 
reliable  means ;  these  means  disagree  with  our  scheme  only  in  lot  26 
and  perhaps  lot  22. 

According  to  tables  17-20,  the  fewer-noded  check  parent  of  each 
check  row  has  usually  given  the  earlier  progeny.  In  fact,  the  agree- 
ment of  parental  and  progeny  differences,  throughout  the  cultures,  is 
decidedly  remarkable.  It  is  unfortunate  that  the  later  parents  were 
always  placed  in  the  east  half  of  the  row,  especially  in  view  of  the 
fact  that  there  was  indication  of  important  differences  in  soil  and 


L919] 


Frost :    Mutation  in  Muttliii>l<i 


L13 


Tabu    L9 
1911,  field;  plants  transplanted  from  greenhouse.     Tim*    from  sowing  to 

i  mi  iii:  net  ii/  earliest  corolla.    Singles. 


Row 

Parent-lot 

internode 

mean 

i...i 

I'n .■nt  .i 
mi.  i  node 
number 

Progens  flowering 
lis   Nov.  :t 

1  ,01 

Pan  ntal 

internode 

number 

Pi  ..>■•  n\ 
1      1 

.,v    3 

Number 

1 iivs  to 

flowering 

\  umbei 

Daj'H  to 

tli.Wrt  nil' 

1 

29.60 

1 

29 

7 

147  14 

2 

32 

7 

128.57 

2 
3 

21.40 

3 

5 

16 

25 

34 

26 

91  94 
119.46 

4 
6 

20 

27 

33 

25 

105.45 
104.08 

4 

49.57 

7 

46 

30 

103.13 

8 

54 

24 

105.67 

5 
6 

7 

27 .  33 

9 
11 
13 

21 
22 

3  1 

30 
33 

18 

91   73 

98.85 

100.67 

10 

12 
14 

21 
25 

11 

34 
27 
13 

91    12 
108  30 

120.62 

8 

28 .  50 

15 

27 

17 

112.94 

16 

29 

18 

118.00 

9 
10 
11 
12 
13 

42 .  56» 

17 
19 
21 
23 
25 

33 
36 
42 
49 
55 

30 
34 
25 
11 
15 

100.27 
97 .  35 
129.36 
122.00 
136.40 

18 
20 
22 
24 
26 

35 
37 
45 
51 

18 
21 
25 
14 
13 

109  67 
117.81 
121.76 
151.57 
121.08 

14 

47.80 

27 

46 

10 

159.40 

28 

56 

8 

162.50 

1  This  parent-lot  value  does  not  apply  to  lot  26,  which  consists  of  progeny  of 
WG9-C10  itself. 

Table  20 
Sinnc  as  table  19,  for  dotibles  flowering  by  August  7. 


Row 

Lot 

Progeny  flowering  by  Aug.  la 

Lot 

Progeny  flowering  by  Aug.  1 

Number 

Days  to  flowering 

Number 

Days  to  flowering 

1 

1 

38 

90.26 

2 

33 

91.03 

2 
3 

3 

5 

36 
39 

80 .  22 
84 .  46 

4 
6 

36 
39 

80.00 
84.10 

4 

7 

36 

81.28 

8 

31 

84.32 

5 
6 

7 

9 
11 
13 

42 
42 
37 

75.86 
77.90 
84.32 

10 
12 
14 

41 
40 
35 

76.59 
80.25 
84.80 

8 

15 

46 

83.87 

16 

33 

85.21 

9 
10 
11 
12 
13 

17 
19 
21 
23 
25 

37 
42 
39 
33 

32 

80.43 
78.24 
85.95 
89.03 
88.56 

18 
20 
22 
24 
26 

34 
39 
30 
26 

21 

84.12 
83.85 
87.93 
88.85 
89.05 

14 

27 

35 

88.97 

28 

29 

90.28 

■  Only  48  more  doubles  altogether  flowered  by  November  3,  and  25  of  these 
were  in  the  even-numbered  lots  20  to  28. 


114 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


probably  in  the  incidence  of  disease,  favoring  the  plants  in  the  west 
half.  The  internode  data  of  1910,  however,  show  a  similar  tendency. 
Small  genetic  differences  are  suggested,  though  it  would  be  remarkable 
if  they  were  so  uniformly  present  in  these  plants  of  a  single  line  of  a 
usually  selfed  species,  descendants  of  parents  and  a  common  grand- 
parent grown  under  glass. 

If  such  differences  exist  in  the  race,  conceivably  some  combination 
due  to  crossing  might  simulate  an  early  mutation.  The  evidence  as  a 
whole,  however,  does  not  favor  such  an  origin  for  our  early  type ;  it  is 
widely  divergent  from  the  Snowflake  type,  and  seems  to  depend  on 
a  single  main  factor  difference  from  Snowflake. 

Table  21 
Cultures  of  1912.     Ancestry  and  parental  data. 


Parental  data 

Lot 

Parent 

Seeds  sown 

Probable  type 

Days  to 
flowering11 

Inter- 
nodesd 

1 

WSI-W0I6 

Snowflake8 

120 . 0 

38 

15 

2 

WG9-C10-W6 

Early 

116.5 

33 

15 

3 

WL10-W>2 

Snowflake 

139 . 5 

51 

15 

4 

WL10-W23 

Snowflake* 

120.5 

38 

15 

5 

WSl-W-d 

Snowflake 

141.5 

57 

15 

6 

WLIO-W2I4 

Snowflake8 

126 . 5 

38 

15 

7 

WL10-Wo7 

Snowflake 

145.5 

54 

15 

8 

WG9-C10-W8 

Early 

129 . 5 

45 

15 

9 

WS1-W.12 

Crenate-leaved  '■'' 

119.5 

34 

7r 

a  Suspected  before  testing  of  belonging  to  the  early  type;   first  parent  also 
tested  in  1910. 

b  A  heterozygote  between  the  crenate-leaved  and  Snowflake  types. 

e  Probably  open  pollinated. 

d  All  the  parents  grew  in  the  same  house  at  the  same  time. 


The  essential  feature  of  the  supplementary  cultures  of  1912,  since 
no  seed  of  WL10  remained,  was  a  test  of  two  pairs  of  early  and  late 
progeny  of  WL10  (lots  3  and  4,  6  and  7,  table  21),  in  comparison  with 
two  control  lots — one  (lot  2)  from  a  known  early  parent,  descended 
from  WG9-C10,  and  one  (lot  5)  from  a  late  descendent  of  WS1. 
Incidentally,  WS1-WJ6  and  WG9-C10-W8  were  retested,  and  the 
few  available  seeds  of  WS1-W,12  were  used  to  test  that  phenotypically 
early  parent. 

The  results  are  given  in  tables  22  and  23  and  chart  4.  The  very 
low  individual  from  WS1-W216  came  from  a  very  weak  embryo,  and 
should  be  disregarded ;  the  exceptionally  high  general  range  of  this 
lot,  which  was  also  visibly  behind  all  others  in  development,  was  prob- 


L919] 


Frost:    Mutaliini  m  Mullhiola 


11.-. 


Table  22 

Cultures  of  1912.     Number  of  main-stem  internodes  below  first  flower-bearing 
node.    Frequency  distributions  for  singles." 


f  Gen.  1 

WSl 

Wl.'i 

WL10 

WSl 

WHO 

WG9 

wsi 

Ann-try   -<    Gen.  2 

Wo  10 

CIO         \> 

f22 

W23 

Wol 

Wo  14 

W27 

CIO 

w2i2 

1   Gen.  3 

W6 

• 

W8 

Internodes 
18  

it 
i" 

2 

1 

2t 

i" 

i 
3 

1 

1 

4 
1 

1 
1 

1 

3 
3 

1 

2" 

1 

2 

1 

It 

i" 
2" 
i" 

19  

. 

20  

21  

22  

23  

24  

25  .. 

26  

27  

28  

It 

29  

2 

It 

30  

31      

32  

3:5     

34  

35  

a  See  note  a  to  table  5. 


Table  23 
Cultures  of  1012.     Same  as  table  22,  for  doubles.* 


[  Gen.  1 

WSl 

w  1  ;n 

\\  1    III 

WSl 

WLIO 

WG9 

WSl 

Ancestry   <    Gen.  2 

Wo  10 

CIO         \ 

V22 

W23 

Wol 

Wo, 14 

V 

V27         CIO 

Wo  12 

1    Gen.  3 

W6 

W8 

Internodes 

12           

1A 

1 

2" 

3t 

l" 

1 

1 

2 
2 
1 

i" 

1 

5 
1 

2" 

3 

i 

i" 

1 

3 

1 

i" 

1'      2 

1  2 
1 

1 

2  1 

3  2 

13  

14  

15  

16  

17  .. 

18  .. 

19  .. 

20  .. 

21  .. 

22  . 

23  . 

It 
3 
3 
2 

24  .. 

25  .. 

1 

26  .. 

1 

27  .. 

28  

It 

29  . 

30  .. 

31 

a  See  note  a  to  table  5. 


116 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


ably  due  to  some  cultural  accident,  perhaps  to  an  excess  of  moisture 
in  this  row  of  pots. 

The  lots  of  plants  may  seem  rather  absurdly  small  for  their  pur- 
pose, but  the  uniformity  of  development  here,  with  the  marked  normal 
divergence  in  internodes  of  the  types  in  question,  seems  to  justify  a 
fair  degree  of  confidence.  Ten  plants  here  were  probably  worth  fifty 
in  the  field. 


31 

r 

ingl 
oubl 

es 

ee 

— 

-- 

30 
29 

i 

1 

27 
26 
25 



1 

< 

» 

___ 

1 



"§  24 
c 

u 

22 

I — < 

►  --J 

21 

1 

1 

20 

19 
18 

17 

16 

< 

1 

W216 

I 
wsi 


W6 

I 
CIO 

I 

WG9 


W22 


W23 


WL10 


W2I  W2H 

'  J — 

WSI  WL10 

Ancestry 


W27 


W8  W2I2 

I  I 

cio       wsi 

I 

WG9 


Chart  4.  Cultures  of  1912.  Internodes:  parental  values  and  progeny  means, 
shown  as  in  chart  1.  The  true  parental  values  are  twice  those  indicated  by  the 
ordinate  figures,  which  apply  directly  to  the  progeny  values. 


This  test,  with  that  of  1910,  shows  very  positively  that  WS1-W216 
was  only  phenotypically  few-noded.  Evidently  WG9-C10-W8,  the 
parent  of  field  lot  22,  really  carried  the  earliness  factor,  as  was  some- 
what doubtfully  inferred  from  the  field  results;  the  five  progeny  of 
WS1-W212,  on  the  other  hand,  though  from  a  fewer-noded  parent, 
have  values  that  make  the  presence  of  the  earliness  factor  improbable. 

On  the  main  point  at  issue  the  evidence  seems  satisfactory.  Neither 
of  the  two  very  early  and  few-noded  progeny  of  "WL10  represented 


1919]  Frost:    Mutation  in  Matthiola  1 17 

shows  in  its  progeny  any  evidence  of  belonging  to  the  early  type;  the 
means  are  slightlj  lower  than  for  the  many-noded  sibs  of  these  parents, 
liui  far  less  so  than  with  the  parents  descended  from  WG9  CIO. 

We  conclude,  thru,  thai  WG9-CK*  was  probably  a  monohybrid, 
and  thai  the  early  bearing  gamete  entering  into  its  composition  was  of 
unknown  bill  presumably  mutative  origin. 

Most  of  the  extracted  Late  or  many-noded  parents  may  now  be 
selected  with  practical  certainty.  WG9-C10-C8  and  CI  i  lots  5  and  6 
in  the  1911F  cultures  and  WG9-C10-M7  and  Ms  Jots  13  and  14) 
were  genetically  very  similar  to  the  check  parents,  as  lias  already  been 
concluded  for  two  of  them  from  the  greenhouse  cultures;  presumably 
they  wnv  pure  Snowflake. 

The  data  for  WG9  CIO  itself  (lot  26)  seem  to  indicate  that  the 
results  from  the  last  eight  lots  are  of  very  doubtful  value;  still,  they 
show,  especially  in  the  original  individual  records,  some  evidence  of  the 
earliness  factor  which  must  be  present  in  part  of  the  individuals.  The 
pour  and  slow  germination  of  the  old  seed  available  may  have  had  an 
important  influence  on  the  result;  many  of  the  early  embryos  may  have 
been  non-viable,  and  the  seedlings  may  have  been  weaker  than  those 
from  fresh  seed.  The  1911  data  and  observation  of  the  plants  in  the 
tield  suggest  that  WG9-C10-AV7,  W3,  and  W10  (lots  23.  24,  and  25) 
are  the  only  remaining  extracted  late  parents,  WG9-C10-W5  and  W8 
(lots  21  and  22)  carrying  the  earliness  factor,  as  the  four  parents  just 
preceding  them  in  the  cultures  obviously  did.  Tables  22  ami  23  con- 
firm this  conclusion  for  WG9-C10-W8. 

It  is  presumably  impossible  to  make  a  positive  separation  of  the 
parents  homozygous  for  the  presence  of  the  early  factor.  The  green- 
house data  suggest  that  WG9-C10-M4  was  a  pure  early  individual ; 
the  field  data  (see  lot  9)  agree,  and  suggest  that  WG9-C10-M9  (lot 
10)  and  perhaps  WG9-C10-M6  (lot  11)  belong  in  the  same  class. 
\V(i!l-C10-C2,  C5,  and  CIO  (lots  3,  4.  and  40)'-  were  all  evidently 
heterozygous.  Of  the  parents  grown  in  house  W,  it  would  seem  that 
only  WG9-C10-W11  (field  lot  19)  was  homozygous  early.  We  have, 
provisionally,  for  the  available  single  progeny  of  WG9-C10: 

House  C  House  M  House  W  Total 

Pure  early 0  3  14 

Hybrid  early 3  15  9 

Pure  late 2  2  3  7 

20 


12  Statistical  data  given  for  the  last  only  for  tlie  1910  cultures,  not  for  this 
field  lot. 


118  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

This  corresponds  well  enough  with  the  monohybrid  expectation  of 
5  :  10  :  5 ;  in  fact,  the  deviation  is  just  such  as  would  be  expected  if  there 
was  occasional  cross  pollination  of  the  unprotected  flowers  of  WG9- 
C10  from  Snowflake  plants.  The  large  proportion  of  evidently  pure 
late  parents  is  strong  evidence  for  the  monohybrid  nature  of  WG9-C10. 

The  proportions  of  the  two  types  among  the  doubles  can  only  be 
estimated.  The  1908  data  suggest  that  5  of  the  10  doubles  there 
reported  were  early ;  this  number,  with  the  13  singles  so  classed,  makes 
a  total  of  18  early-type  plants  out  of  30.  The  ratio  is  slightly  nearer 
to  1 : 1  than  to  3:1,  and  the  former  proportion  would  suggest  the 
peculiar  type  of  inheritance  found  with  the  mutant  types  yet  to  be 
described.  The  evidence  of  the  1910  distributions,  however,  shows  that 
the  early  type  largely  predominates  in  the  next  generation  with  both 
singles  and  doubles,  and  apparently  this  is  true  even  when  we  exclude 
the  progeny  of  the  one  parent  classed  as  pure  early. 

The  early  factor  can  be  positively  detected  only  by  progeny  tests. 
No  test  has  shown  the  presence  of  this  factor  elsewhere  than  in  WG9- 
C10  and  part  of  its  descendants.  WG9-C10  produced  the  early  and 
Snowflake  types  among  20  single  progeny  nearly  in  the  typical  mono- 
hybrid  proportions.  Inspection  of  the  double  progeny  in  two  genera- 
tions suggests  similar  or  possibly  somewhat  lower  proportions  there. 
A  vicinistic  origin  for  WG9-C10  is  improbable.  Presumably,  then, 
the  early  type  arose  from  Snowflake  by  a  single  factor  mutation,  the 
dominant  mutant  factor  being  inherited  without  special  complications. 
We  shall  now  consider  certain  apparently  mutant  types  which  are 
characterized  by  peculiar  genetic  behavior. 

2.  THE  SMOOTH-LEAVED  TYPE 

This  type  was  first  observed  in  the  cultures  of  1908  (table  1)  and 
has  occurred  frequently  in  later  cultures  (table  3).  It  is  perhaps  the 
mutant  type  of  most  frequent  occurrence  among  progeny  of  Snow- 
flake  or  early  parents ;  2410  unselected  progeny  from  house-sown  seed 
of  such  parents  (see  table  28)  included  28  apparent  mutants  (14 
singles,  11  doubles,  and  3  undetermined),  a  mutation  coefficient  of 
1.16  ±  .15  per  cent. 

As  grown  in  the  greenhouse  at  Ithaca,  this  type  (fig.  7,  tables  12 
and  13)  was  often  many-noded,  with  correspondingly  late  flowering. 
Its  most  striking  peculiarity,  shown  especially  by  young  seedlings  and 
not  evident  in  the  figures,  was  a  lack  of  buckling  between  the  veins 


l!M!»j 


Frost:    Mutation  in  Matthiola 


119 


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120  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

of  the  leaves,  and  of  general  convexity  of  the  upper  surface  of  the 
leaves.  Mature  plants  developed  under  favorable  conditions  in  the 
greenhouse  closely  resembled  Snowflake ;  the  leaves,  however,  were 
noticeably  brittle,  and  the  dry  capsules  so  brittle  that  it  was  often 
necessary,  as  it  was  not  with  Snowflake,  to  shell  the  seeds  individually. 
Probably  the  fibrovascular  system  is  in  some  way  defective;  Oenothera 
rubrinervis,  which  is  also  brittle  (de  Vries,  1906,  lecture  18),  has 
thin-walled  bast  fibers. 

In  the  field  cultures,  both  at  Ithaca  (fig.  5)  and  at  Riverside,  under 
conditions  less  favorable  on  the  whole  to  the  initiation  of  flowering, 
this  type  (fig.  8)  differed  much  more  widely  from  Snowflake.  Flower- 
ing was  excessively  delayed,  and  the  plants  often  remained  low,  with 
few  branches,  and  rosette-like,  with  thin,  rather  narrow  leaves.  Small 
brown  dead  spots,  possibly  due  to  excessive  transpiration,  occurred  so 
frequently  on  the  leaves  as  to  constitute  a  good  diagnostic  character 
for  the  type.  Another  peculiarity  observed  in  the  field  is  a  reflexed 
position  of  the  tip  of  the  young  leaf  when  first  visible — Snowflake 
leaves  being  completely  erect  from  the  first. 

In  the  1914  cultures,  with  better  development  than  in  other  field 
cultures,  some  smooth-leaved  plants  (figs.  9  and  10)  were  again  more 
like  Snowflake.  though  later  and  evidently  more  leafy. 

Six  smooth-leaved  parents  have  been  used  in  progeny  tests,  three 
of  these  being  apparent  mutants  and  three  being  Ft  progeny  of  two 
of  those  mutants.  The  results  are  presented  in  tables  24  and  25 ;  these 
tables  require  a  brief  explanation,  which  will  apply  also  to  the  similar 
tables  for  other  types-. 

For  the  plan  of  the  new  pedigree  numbers  here  used,  see  "Methods. " 
The  initial  plants  of  a  series  are  designated  as  the  Pl  generation  in 
the  tables,  their  progeny  as  F,,  etc.  In  table  24  the  cultures  are 
arranged  according  to  their  generations  and  their  pedigree  numbers 
under  each  generation ;  the  smooth-leaved  parents  (P1  or  of  the  Px 
type)  are  given  first,  followed  by  the  extracted  Snowflake  parents. 
In  table  25  "good  germination"  indicates  that  in  all  lots  included 
(taken  as  grown,  not  as  summed  by  parents  in  table  24)  the  number 
of  plants  determined  exceeds  50  per  cent  of  the  number  of  seeds  sown, 
and  vice  versa;  the  weighted  mean  percentages  obtained  by  dividing 
the  total  numbers  of  plants  by  the  respective  total  numbers  of  seeds 
are  given  for  each  table  in  a  footnote. 

All  six  smooth-leaved  parents  (tables  24  and  25)  gave  mixed 
progeny,   part   smooth-leaved   and   part   Snowflake.      The   surprising 


L919] 


Frost:    Mutation  in  Miiiihioiu 


121 


fact  is  that  the  parental  (smooth-leaved)  type  appears  not  in  three- 
fourths  of  tlic  progeny,  hut  in  only  about  one-fourth. 

The  extracted  Snowflake  parents  tested  behave  like  pure  recessives, 
showing   no   influence   of    their   smooth-leaved   ancestry.      Only    the 
aberranl  ratio  seems  inconsistent  with  the  assumption  thai  the  smooth 
leaved   individuals  tested  were  ordinary  heterozygous  dominants. 

The  relatively  weak  growth  of  this  type  and  the  apparently  poor 
germination  of  the  seed  produced  hy  il  suggest  thai  normal  segregation 
may  be  masked  by  selective  elimination.     Possibly  the  smooth-leaved 


Table  25 
Smooth-leaved  type:  heredity,    nummary. 


Progeny 

Plants 

Parents 

Total   examined 

Smooth-leaved 

Cultures 

Seeds 

Undeter- 

Deter- 

mined 

mined  , 

Number 

Per  cent 

All  smooth- 

leaved 

Ithaca 

304,0/7 

7 

156 

40 

25.6  ±   2.4 

All  smooth- 

leaved 

Riverside 

196 

I 

78 

23  (24) 

30.8   ±3.4 

All  smooth- 

leaved  (6) 

All 

500,  277 

8 

234 

63  (64) 

27.4   ±    2.0 

All  Pi  smooth- 

leaved  (3) 

All 

244,  m 

3 

115 

32 

27.8   ±    2.8 

All  Fi  smooth- 

leaved  (3) 

All 

256 

5 

119 

31  (32) 

26.9   =*=   2.8 

All  smooth- 

Germination 

leaved 

good 

293, 138 

8 

187" 

55  (56) 

29.9  ±   2.2 

All  smooth- 

Germinal  ion 

leaved 

poor 

207,  7.9 

0 

47a 

8 

17.0  *   4.4 

All  Snowflake 

(5,  F,  and  F2) 

All 

208,  50 

2 

173    • 

0 

0 

■  Respectively  63.8  and  22.7  per  cent  of  the  numbers  of  seeds  planted. 

factor  is  lethal  when  homozygous,  as  is  often  the  case  (Muller,  1918) 
with  dominant  mutant  factors  in  DrosopJrila;  the  data  for  germi- 
nation, however,  indicate  that  two-thirds  of  the  mature  embryos  can 
hardly  belong  to  the  mutant  type.  We  might  expect,  in  view  of  the 
weak  growth  of  smooth-leaved  plants,  that  partial  elimination  of 
heterozygotes  would  also  occur.  That  this  is  the  case  is  suggested, 
though  the  numbers  are  small,  by  the  lower  proportion  of  the  mutant 
type  with  poor  germination  (table  25;  see  also  tables  39  and  40)  ;  it 
should  he  noted,  however,  that  transferring  the  first  lot  of  table  24, 
the  only  lot  between  50  and  73  per  cent,  to  the  "poor"  total,  makes 
the  percentages  practically  identical.13 


,:;  See  also  table  2  ami  the  second  paragraph  under  "Occurrence  of  Mutants." 


122  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

In  connection  with  the  question  of  lethal  action  we  must  consider 
the  inheritance  of  doubleness  of  flowers.  Snowflake  seed  regularly 
gives  a  mixture  of  singles  and  doubles,  about  53  per  cent  being  doubles. 
The  doubles,  which  are  totally  sterile,  are  probably  (Frost,  1915)  pure 
recessives  (dd)  for  a  single-double  factor  pair.  The  singles  are  always 
heterozygous  (Dd)  ;  crosses  with  pure  single  races  (Saunders,  1911) 
show  that  the  approximately  1 : 1  ratio  and  the  failure  to  produce  pure 
singles,  with  self  pollination,  are  due  to  the  fact  that  all  the  functional 
pollen  is  doubleness-carrying  (d) .  The  excess  of  doubles  over  50  per 
cent  has  been  explained  by  Miss  Saunders  (1911)  as  due  to  hetero- 
zygosis of  the  singles  for  two  linked  complementary  factors  necessary 
to  singleness,  and  by  the  present  writer  (Frost,  1915)  as  due  to  lower 
viability  of  the  "single"  gametes  or  embryos.  The  absence  of  func- 
tional single-carrying  pollen  is  apparently  due  to  a  lethal  factor  acting 
after  separation  of  the  microspore  tetrads,  since  the  tetrads  themselves 
appear  normal. 

In  any  consideration  of  factors  linked  with  the  single-double  pair, 
this  semisterility  of  the  pollen  must  be  remembered.  For  example, 
any  dominant  factor  completely  coupled  with  D  in  pollen  formation 
would  be  totally  absent  from  the  functional  pollen,  and  the  zygotes 
produced  by  selfing  would  show  directly  the  strength  of  linkage  in  the 
ovules. 

The  available  data  for  the  smooth-leaved  type  (table  24)  are  far 
from  constituting  an  adequate  test  of  linkage,  but  they  suggest  that 
the  factors  are  independent.  Certainly  no  high  degree  of  linkage  is 
indicated  by  the  totals,  nor  do  the  detailed  data  suggest  that  smooth- 
leavedness  is  coupled  with  singleness  in  some  parents  and  with  double- 
ness in  others. 

We  must  admit  that  the  peculiar  inheritance  of  this  type  is  not 
yet  positively  explained.  Evidently  larger  cultures  are  needed,  and 
crossing  with  the  Snowflake  type  and  with  other  commercial  varieties; 
cytological  study  may  also  be  required.  Certain  comparisons  and 
speculative  possibilities  deserve  mention,  however,  especially  since  the 
types  yet  to  be  discussed  furnish  additional  evidence  bearing  on  them, 
We  may  compare  the  smooth-leaved  and  double  types,  as  follows : 

Double  Smooth-leaved 

1.  A  rare  mutation  of  pure  single  1.  Apparently  a  common  mutation 

("normal").  of  pure  Snowflake  ("normal"). 

2.  Eecessive;  extracted  recessives  2.  Apparently  dominant ;  extracted 

are  sterile  mutant-type  plants.  recessives    are    fertile    normal 

plants. 


L9191 


Frost:   Mutation  in  MuiiIikiIu 


123 


BI.E 

3.  Homozygous  dominants  nol  pro- 
duced by  h\  brids,  because  func- 
t  ional   pollen  ca  1 1  issive 

factor  only. 

i.   Recessive    (mutant)    type    the 
more  vigorous. 


Dominant  factor  or  another  fac 
tor  \  i'i\  closely  linked  with  it 
is  incompatible  with  formation 
of  functional  pollen. 

Recessive  type  exceeds  the  ex- 
pected equality  by  about  .'!  per 
cent  among  some  7000  indi- 
vidua  Is. 


Smo  i  1 1> 

3    I  tamo  j : a  dominants  perhaps 

not  produced  by  hybrids.1 ' 


i.   Recess  i\  e    I  normal  i    type    i  he 
more  vigorous;  difference  much 
i  ea  ter  t han   with   single  and 
double. 

5.  Relation    Of   dominant    factor   to 

\  lability  of  pollen  not  yet  de- 
termined. 

6.  Recessive  type  exceeds  equality 

by   about   215   per   cent   among 
234   individuals. 


The  mosl  probable  hypothesis  for  smooth-leavedness,  then,  would  so 
Ear  seem  to  be  essentially  the  same  as  for  doubleness — complete  elimina- 
tion of  the  weaker  type  in  pollen  formation,  and  partial  elimination  in 
embryo-sac  formation.  Reciprocal  crosses  with  Snowflake  arc  obviously 
necessary;  as  we  shall  soon  sec,  three  of  the  other  mutant  types  have 
already  proved  to  &<  carried  bg  both  eggs  and  sperms. 

The  case  of  Oenothera  lata  (Gates,  1915)  suggests  the  possibility 
that  the  smooth-leaved  form  might  arise  by  reduplication  of  a  chromo- 
some With  ordinary  0.  lata  the  pollen  is  sterile,  but  pollination  by 
0.  lamarckiana  gives  about  15-20  per  cent  of  lata.  This  deficiency  of 
lata  individuals  is  due,  it  seems,  to  a  frequent  loss  of  the  extra 
chromosome  at  meiosis  in  lata  ovules,  with  a  resulting  formation  of 
more  than  50  per  cent  of  seven-chromosome  (lamarckiana)  eggs. 

If  the  smooth-leaved  type  originates  through  duplication  of  a 
chromosome,  we  might  suppose  that  other  types  of  similar  heredity 
involve  other  pairs  of  chromosomes.  The  apparent  parallel  with 
O.  lata,  which  Bartletl  l  1917)  has  noted,  was  long  ago  suggested  by 
the  data,  but  with  at  least  two  or  three  type's  to  be  described  linkage 
phenomena  have  seemed  to  conflict  with  this  interpretation.  Possibly 
different  processes  have  produced  different  mutant  types  as  with 
Oenothera;  as  we  have  considered  types  suggestive  of  O.  rubrinervis 
(early  i  and  of  O.  lata  (smooth-leaved),  we  may  consider  next  a  form 
which  in  appearance  is  remarkably  suggestive  of  O.  gigas. 


it  This  possibility  is  only  suggested  by  these  cultures,  but  it  becomes  highly 
probable  when  the  data  for  other  types  are  considered. 


124 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 


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L919]  Frost:    Mutation  in  Matthiola  125 

It  should,  however,  firsl  b<  aoted  that,  as  will  appear  Later,  phe- 
nomena of  apparenl  Linkage  in  the  case  of  certain  other  types  (crenate, 
slender,  and  narrow)  suggesl  thai  these  forms  commonly  arise  from 
Snowflake  by  segregation  rather  than  1>.\  immediate  mutation.  The 
obvious  objection  to  this  hypothesis  is  the  fad  thai  the  apparently 
mutant  t\  pes  seem  to  be  dominant  to  the  "normal"  or  Snowflake  t\  pe. 
Tins  objection  can  be  met  by  assuming  the  presence  o!"  dominant  in- 
hibiting  fat-tors  in  the  Snowflake  parents  thai  give  apparent  mutants.15 

If  the  apparenl  mutants  of  the  smooth-leaved  type  arc  thus  pro- 
duced by  crossing  over  in  a  sel  of  balanced  factors,  the  lethal  "balanc- 
ing" the  smooth-leaved  factor  itself  may  be  distinct  from  thai  winch 
sterilizes  the  singleness-carrying  pollen.  In  considering  the  results 
here  reported,  therefore,  we  must  always  bear  in  mind  the  possible 
presence  of  several  unidentified  lethal  factors.  If  the  apparent  absence 
of  linkage  between  the  smooth  and  double  factors  is  not  misleading,  we 
must  suppose  that  these  factors  are  carried  by  different  pairs  of 
chromosomes;  considerations  advanced  by  Muller  (1918,  pp.  479-482), 
however,  make  it  rather  probable  that  the  commoner  types  of  apparenl 
mutants  here  discussed  are  all  due  to  factors  carried  by  one  pair  of 
chromosomes,  the  pair  containing  the  factor  for  doubleness  and  its 
normal  allelomorph. 

3.  THE  LARGE-LEAVED  TYPE 

A  double  of  this  type  probably  occurred  in  the  1907  cultures, 
though  its  appearance  attracted  so  little  attention  that  no  record  was 
made.  In  the  field  cultures  of  1911  (table  3)  several  individuals  sug- 
gested a  gigas  type,  though  there  seemed  to  be  intergradation  with 
Snowflake.  In  the  1912  cultures  a  single  with  leaves  "long,  rather 
narrow',  thick"  developed  normally  and  produced  an  abundance  of 
good,  seed;  from  this  individual  (28a)  all  cultures  of  this  type  are 
descended. 

This  type  is  stout  and  coarse  throughout,  and  late  to  flower.  The 
leaves  are  strikingly  long,  thick,  and  rigid,  though  as  a  rule  relatively 


1S  A  letter  suggesting  this  explanation  was  received  from  Dr.  Muller  soon 
after  the  same  idea  had  been  outlined  in  the  "General  Discussion"  section  below. 
Dr.  Muller  kindly  gave  further  attention  to  difficulties  at  first  encountered  by 
the  present  writer,  materially  assisting  in  the  formulation  of  an  apparently 
tenable  form  of  the  hypothesis.  Since,  however,  this  scheme  may  seem  "far- 
fetched" and  unduly  complex,  it  appears  desirable  to  leave  the  original  discus- 
sion of  the  individual  types  substantially  unchanged.  When  the  difficulties 
encountered  by  the  assumption  of  frequent  true  mutation  have  been  more  fully 
presented,  the  need  for  some  such  addition  to  the  scheme  will  be  more  evident. 


126 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


narrow  ;  under  unfavorable  weather  conditions  the  flowers  are  often  few 
and  defective,  while  the  leaves  are  resistant  and  long-lived  (fig.  11). 
Figures  12  and  13  show  well  the  coarse  leaves  and  lateness  of  well 
developed  large-leaved  plants  in  the  1915-16  cultures,  the  plants  in 
the  latter  figure  being  several  weeks  the  older. 

The  results  of  the  progeny  tests  are  given  in  tables  26  and  27.  All 
the  twenty  large-leaved  individuals  tested  have  given  mixed  progeny; 
the  proportion  of  the  mutant  type,  though  much  larger  than  with 


Table  27 
Large-leaved  type:  heredity.     Suihmary. 


Progeny 

Plants 

Parents 

Total   examined 

Lame-leaved 

Cultures 

Seeds8 

mined 

mined 

Number 

Per  cent 

28a 

1913,1914, 

&  1915-16 

122 

2 

73 

38  (40) 

54.8  ±   3.9 

28a-F,  (3) 

1914 

120 

2 

40 

14(19) 

47.5  ±   5.3 

28a-F,  (12) 

1915-16 

288 

2 

190 

76  (90) 

47.4  ±   2.4 

28a-F,  (4) 

1915-16 

90 

0 

54 

25  (26) 

48.1   =*=   4.6 

28a-F,  &  F2  (19) 

All 

498 

4 

284 

115(135) 

47.5   *    2.0 

All  large-leaved 

(20) 

All 

620 

6 

357 

153  (175) 

49.0  ±    1.8 

Large-leaved 

Germination 

good 

360 

3 

260b 

115(131) 

50.4   ±   2.1 

Large-leaved 

Germination 

poor 

260 

3 

97" 

38  (44) 

45.4   ±    3.4 

Snowflake  (1,F,) 

1915-16 

24 

0 

15 

0 

0 

a  Mainly  from  unguarded  flowers;  see  table  26. 

b  Respectively  72.2  and  37.3  per  cent  of  the  numbers  of  seeds  planted. 

smooth-leaved,  approximates  to  50  per  cent,  not  75  per  cent,  with  little 
indication  of  selective  elimination  with  poor  germination.10 

Here  plainly,  as  with  smooth-leaved,  no  pure  mutant-type  parent 
has  yet  been  tested.  Since  this  is  also  true  of  the  other  types,  aside 
from  early,  that  have  been  somewhat  extensively  tested,  and  fifty-three 
mutant-type  parents  in  all  have  given  Snowflake  progeny,  it  is  prob- 
able that  homozygous  individuals  of  these  types  seldom  or  never 
develop.  The  actual  adult  ratio  with  large-leaved  is  plainly  not  2 : 1, 
but  rather  1 : 1,  a  fact  that  would  suggest  absence  of  the  mutant-type 
factor  or  factors  from  the  pollen.  The  small  trial  cultures  started 
in  1917,  however,  show  that  the  type  is  carried  by  both  sperm  and 
eggs. 


is  Since  hybrids  are  of  the  mutant  type  in  appearance,  the  possible  cross 
pollination  by  Snowflake  parents  could  hardly  give  Snowflake  progeny  with  any 
pure  large-leaved  parent.  It  may,  however,  have  reduced  slightly  the  proportion 
of  large-leaved  progeny  from  heterozygous  parents  of  this  type. 


1919] 


Frost:    Mutation   in    Mattliiola 


127 


If  we  are  dealing  here  with  a  type  cytologically  like  Oenothera 
gigas,  or   rather   the    triploid   semigigas,  abnormal    distributions   of 

chromosomes  may  occur  at  mciosis,  giving  unpredictable  genetic 
results.  There  has  been  special  difficulty,  as  the  numbers  of  doubtful 
individuals  in  table  26  suggest,  in  separating  large-leaved  from  Snow- 
flake,  though  in  part  of  the  cases  the  difference  is  extreme.  Possibly 
some  of  the  doubtful  individuals  are  genetic  intermediates  due  to 
irregular  meiosis  in  triploid  nuclei;  such  irregularities  in  division 
(Gates,  1915)  occur  with  Oenothera.  Both  cytological  examination 
and  crosses  with  Snowflake  are  plainly  required. 

Table  28 

Crenate-leaved  type:  numbers  of  apparent  mutants  and  association  of  the 
type  with  singleness  of  flowers. 


Progeny  of  Snowflake  and  early  parents 

Crenate-leaved 

Culture 

Total 
examined" 

Coefficient  of 

Single 

Double 

All 

mutation 

1908 

725" 

6 

1 

7 

.97  ±    .22 

1010 

338 

3 

0 

3 

.89  =*=    .32 

1911F,  seed  house- 

sown 

2072 

13 

3 

16 

.77   ±    .13 

All  above 

3135 

22 

4 

26 

.83  ±    .11 

All  unselected 

2410 

16 

3 

19 

.79  =«=    .12 

a  See  note  b  to  table  2. 
b  See  note  c  to  table  1. 


4.  THE  CRENATE-LEAVED  TYPE 

This  type  (tables  1  and  3)  is  one  of  the  three  aberrant  types  of 
most  frequent  occurrence  in  the  cultures  here  described,  having  con- 
st it  uted  (table  28)  about  .79  per  cent  of  the  progeny  of  Snowflake 
and  early  parents.  A  large  majority  of  the  individuals  have  been 
singles,  as  table  28  shows.  If  the  apparent  mutants  are  produced  by 
some  process  of  segregation  of  factors,  evidently  the  crenate  and  single 
factors  were  usually  coupled  in  this  material;  if  they  are  produced 
by  immediate  factor  mutation,  or  are  individually  due  to  some  change 
in  a  particular  locus,  evidently  that  locus  is  linked  with  the  single- 
double  locus  and  the  change  is  more  frequent  in  the  single-carrying 
chromosomes ;  and  finally,  if  they  are  due  to  reduplication  or  loss  of 
a  chromosome,  the  apparent  linkage  remains  to  be  explained. 

The  margins  of  Snowflake  leaves  vary  from  entire  or  slightly 
sinuate  to  coarsely  and  irregularly  dentate  or  serrate,  this  character- 
istic being  subject  to  much  environmental  modification  and  varying 


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130  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

with  the  position  of  the  leaves  on  the  plant.  In  the  crenate-leaved 
type  this  character  is  much  accentuated,  as  can  be  seen  by  comparing 
figure  14  with  figures  1  and  3 ;  a  warm  greenhouse  (fig.  14,  upper  line) 
gave  very  marked  serration,  while  a  cool  greenhouse  (lower  plant,  and 
also  fig.  15)  produced  leaves  much  more  nearly  entire. 

Under  the  much  more  extreme  conditions  of  insolation,  temperature, 
and  humidity  at  Riverside,  this  type  was  often  much  dwarfed  in  com- 
parison with  Snowflake  (figs.  16  and  17;  see  also  fig.  23).  In  general, 
growth  is  weaker  than  with  Snowflake  and  the  stems  more  slender. 
Buds  and  flowers  are  often  produced  in  great  abundance,  but  the 
capsules  are  relatively  few,  small,  and  few-seeded.  See  tables  12  and 
13  for  internode  data. 

The  progeny  tests  (table  29)  show  a  slightly  higher  proportion  of 
mutant-type  progeny  than  occurred  with  smooth-leaved.  A  striking 
new  feature  appears  for  the  first  time  in  these  results,  the  regular 
presence  of  linkage,  or  an  association  simulating  linkage,  with  the 
single-double  allelomorphs.  Further,  in  all  the  four  apparent  mutants 
tested  the  crenate  factor  seems  to  be  coupled  with  singleness,  while 
among  the  sixteen  Ft  and  F2  crenate  parents  there  seem  to  be  no 
crossovers.17  We  seem  to  be  justified,  for  reasons  just  given,  in 
summing  th&  progeny  as  in  the  tables.  Two  things  appear  at  once  in 
table  29:  (1)  there  is  a  great  excess  of  total  doubles  over  the  usual 
53  pe^r  cent;  (2)  there  is  a  much  greater  excess  of  doubles  with  Snow- 
flake  than  of  singles  with  crenate;  (3)  the  supposed  double-recessive 
class  (Snowflake  double)  is  about  two  and  one-half  times  as  large  as 
the  double-dominant  class  (crenate  single). 

Table  30  adds  two  features  of  special  interest.  First,  there  is  good 
evidence  of  selective  elimination  with  poor  germination ;  compare  the 
remaining  percentages  with  those  for  "Ithaca,  field,"  "1915,"  "P,," 
and  "Germination  poor,"  and  see  tables  39  and  40;  the  only  excep- 
tional case  is  the  low  percentage  for  the  thirty  plants  of  1915-16.  It 
would  be  surprising  if  the  slow  and  weak  growth  of  the  crenate  plants 
did  not  lead  to  such  a  result.  Second,  there  is  evidence  that  the 
crenate  individuals  are  smaller  than  Snowflake  even  before  germina- 
tion. The  seeds  of  crenate  parents  are  less  uniform  in  size  than  those 
of  Snowflake  parents ;  small  seeds  are  numerous,  and  even  the  larger 
ones  probably  weigh  decidedly  less  than  normal  Snowflake  seeds. 
With  five  crenate  parents  included  in  the  cultures  of  1913,  random 


if  With  four  of  the  parents  the  tests  are  obviously  entirely  inadequate;  one 
other,  22d-9,  gives  no  indication  of  linkage  among  nineteen  progeny. 


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132 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


samples  of  seed  were  sorted,  and  the  smaller  and  larger  seeds  planted 
separately. 

Table  31  gives  the  data  from  this  test.  Here  is  practically  con- 
clusive evidence  (see  tables  39  and  40)  that  the  smaller  seeds  much 
more  often  contain  embryos  of  the  crenate  type.18  Since  the  embryo 
of  a  Matthiola  seed  occupies  practically  all  the  space  within  the  seed 
coats,   it  is   evident  that  even  as  embryos   Snowflake  plants   exceed 

Table  31 

Cultures  of  19] 3.    Crenate-leaved  type:  proportions  from  smaller  and  larger 

seeds  of  crenate  parents. 


Seeds 

Progeny 

Parent 

Total 
deter- 
mined 

„      n^n  , , 

Oren 

Snowflake 

Other 

Size 

Number 

Number 

Per  cent 

types 

22a-l 

Smaller 

21 

6 

4(5) 

83.3    ± 

12.9 

0 

1 

22a-l 

Larger 

29 

23 

3 

13.0   ± 

6.6 

19  (20) 

0 

22a-5 

Smaller 

17 

11 

4 

36.4   ± 

9.5 

6 

1 

22a-5 

Larger 

33 

28 

2 

7.1    ± 

6.0 

25 

1 

22b 

Smaller 

13 

8 

5 

62.5   ± 

11.2 

3 

0 

22b 

Larger 

36 

31 

4 

12.9   =*= 

5.7 

25  (27) 

0 

22d-12 

Smaller 

30 

24 

17 

70.8   ± 

6.5 

5 

2 

22d-12 

Larger 

70 

57 

11(12) 

21.1  ± 

4.2 

42  (44) 

1 

22d-15 

Smaller 

32 

24 

17 

70.8   ± 

6.5 

3 

2(4) 

22d-15 

Larger 

68 

54 

18 

33.3  ± 

4.3 

34  (35) 

1 

All 

Smaller 

113 

73" 

47  (48) 

65.8  ± 

3.7 

17 

6(8) 

All 

Larger 

236 

193" 

38  (39) 

20.2  ± 

2.3 

145(151) 

3 

All 

All 

349 

266 

85  (87) 

32.7   ± 

1.9 

162(168) 

9(11) 

Respectively  64.6  and  81.8  per  cent  of  the  numbers  of  seeds  planted. 


crenate  plants  in  size.  This  fact,  obviously,  is  further  evidence  in 
favor  of  the  hypothesis  of  partial  selective  elimination  of  crenate 
heterozygotes  during  embryonic  development. 

It  may  be  worth  noting  that  the  73  plants  from  the  smaller  seeds 
include  6  (8)  apparent  mutants  of  other  types  (mutation  coefficient 
11.0  per  cent),  while  the  193  plants  from  the  larger  seeds  include 
only  3  apparent  mutants  (1.6  per  cent). 

Before  we  can  profitably  discuss  these  data  further,  we  must  con- 
sider the  results  from  cross  pollination  (tables  32  and  33).  The 
numbers,  though  small,  make  it  very  probable  that  both  eggs  and  sperms 
carry  the  crenate  factor.  Further,  it  appears  from  series  20  that  only 
a  small  portion  of  the  sperms  carry  this  factor,  as  we  should  expect 
from  its  apparent  linkage  with  singleness.  If  homozygotes  are  non- 
viable, the  combined  crenate  percentages  of  reciprocal  crosses  should 


18  The  poorer  germination  of  the  smaller  seeds  suggests  that  the  disparity 
between  the  two  lots  of  seeds  in  the  proportion  of  crenate  embryos  was  even 
greater  than  the  cultures  indicate. 


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University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 


exceed  the  percentage  from  selfed  parents ;  the  expected  high  pro- 
portion with  series  21,  however,  might  well  be  realized  with  adequate 
numbers  and  good  germination. 

In  spite  of  the  small  totals,  it  is  very  probable  that  linkage  similar 
to  that  of  the  selfed  cultures  prevails  with  series  21.  Where  the 
crenate  type  is  the  pollen  parent  (series  20)  linkage  ratios  are  on  our 
hypothesis  impossible,  since  the  eggs  are  all  Snowflake  and  the  sperms 
all  double ;  the  data,  however,  though  statistically  inconclusive,  sug- 
gest that  the  excess  of  singles  with  crenate  and  of  doubles  with  Snow- 
flake  is  greatly  reduced  but  not  abolished. 


Table  33 
Hybridization  of  the  Snowflake  and  crenate-leaved  types.     Summary. 


Progeny 

Cultures 

Seeds 

Plants 

Parents 

Total   examined 

Crenate 

Undeter- 
mined 

Deter- 
mined 

Number 

Per  cent 

20aa,  bb,  &  cb 
20dc,  ed,  &  ic 
20de,ff,gf,gg,&hd 
All  of  series  20 
21aa,  bb,  &dd 
Snowflake    par- 
ents of  hybrid* 
(5) 

1913 

1914 

1915-16 

All 

All 

All 

123 
163 

120 

406 

75 

271,50 

5 
0 
0 
5 
1 

3 

93 

14 

103 

210 

25 

134 

•5(6) 
0 
6 
11  (12) 
2(3) 

(1) 

6.5  ±    1.6 
0 

5.8  =*=   1.5 

5.7   *    1.1 

12.0   *   4.4 

.7  *      .5 

If  we  may  ignore  the  doubtful  correlation  just  mentioned  a  fairly 
adequate  complete  hypothesis  for  the  selfing  ratio  is  possible.  Assume 
(1)  a  gametic  ratio19  of  5DC  :ldC  ADc  :5dc,  or  16%  per  cent  of 
crossing  over ;  (2)  non-viability  of  homozygous  crenate  (CC)  ;  (3)  low 
viability  of  simplex  crenate  (Cc),  eliminating  an  average  of  60  per 
cent  of  this  type;  and  (4)  coupling  of  D  and  C  in  all  parents  tested. 
Evidence  has  already  been  presented  for  assumptions  (1),  (2),  and 
(3),  except  as  to  the  intensity  of  linkage,  while  (4),  as  will  be  seen, 
is  not  at  all  improbable. 

Random  fertilization  under  these  conditions,  excepting  (3),  would 
give  26DdCc  (crenate  single)  -f-  lOddCc  (crenate  double)  -4-  5Ddcc 
(Snowflake  single)  -f-  25ddcc  (Snowflake  double).  The  other  two 
classes,  5DdCC  and  lddCC,  would  be  non-viable  pure  crenate.  Adding 
assumption  (3)  gives  the  following  comparison: 


10  Kepresenting  the  singleness  and  doubleness  factors  by  D  and  d,  and  the 
crenate  factor  and  its  ''normal"  allelomorph  by  C  and  c. 


I '.' in  I  Frost:    Mutation  in  Matthiola  L35 

DdCc  ddCc  Ddco  ddcc 

Theoretical  ratio  (h  =  44.4) 10.4  4  5  25 

Calculated  for  n  =  540 L26  4<t  til  304 

Observed  (n:    540)w. 125  51  57  307 

This  fit  surely  earxnol  be  criticised,  whatever  may  be  thought  of 
the  devices  employed  to  obtain  it!  With  cross  pollination  the  agree- 
ment is  fairly  good  in  the  ease  of  series  20.  which  gives  the  only  fairly 
reliable  data.  We  are  assuming  16%  per  cenl  of  crossover  dC  sperms; 
elimination  of  .60  of  16%  per  cent,  or  10  per  cent  of  the  total,  gives 
.06%/.90  =  7.4  per  cent  expected  crenate,  as  against  5.9  per  cent 
observed.  Series  21  is  supposed  to  have  50  per  cent  of  C  eggs  in 
the  ratio  5DC:ldC;  elimination  of  .60  of  this  proportion,  or  30  per 
cent  of  the  total,  would  leave  .20/.70  =  28.6  per  cent,  against  12.0 
per  cent  in  the  very  inadequate  material  observed.  An  adequate  test 
of  the  hypothesis  obviously  requires  large  hybrid  cultures,  from 
vigorous  seed  sown  under  favorable  conditions  for  germination. 

A  scarcity  of  crossover  crenate  singles  follows  from  the  hypothesis; 
they  constitute  only  one  twenty-sixth  of  the  total  number  of  viable 
crenate  single  progeny  of  crenate  parents.  No  direct  evidence  indi- 
cating that  the  crenate  and  double  factors  are  ever  coupled  in  singles 
has  yet  been  discovered. 

If  the  supposed  crenate  mutants  are  due  to  immediate  factor  muta- 
tion, however,  it  seems  strange  that  the  same  locus  is  changed  more 
readily  in  a  singleness  chromosome  than  in  one  carrying  the  doubleness 
factor,  in  a  ratio  similar  to  the  linkage  ratio  of  later  generations. 
If  the  apparent  mutants  are  really  segregates  from  a  balanced-lethal 
combination,  the  observed  original  coupling  of  crenate  with  single 
might  be  an  accident  of  sampling  involved  in  the  original  choice  of 
material ;  other  initial  parents  might  give  the  reverse  coupling. 

5.  THE  SLENDER  TYPE 

This  type  is  comparatively  rare  as  an  apparent  mutant  from  Snow- 
flake  or  early;  the  3135  plants  reported  in  table  28  gave  only  4  (6) 
mutants  (2  singles  and  4  doubles,  2  of  the  latter  perhaps  Snowflake), 
a  mutation  coefficient  not  over  .19  per  cent.  This  type  seems  to  occur 
more  frequently  among  progeny  of  crenate,  a  type  similar  in  some 


20  Omitting  29  plants  classed  as  neither  crenate  nor  Snowflake,  which  as 
probably  non-crenate  should  perhaps  be  added  to  Snowflake,  and  also  64  plants 
(13  crenate  and  .11  Snowflake)  with  flower  data  incomplete.  Complete  data  for 
the  total  of  633  plants  would  plainly  give  a  somewhat  poorer  fit,  but  this  could 
be  improved  by  assuming  a  slightly  greater  elimination  of  Ccii  zygotes. 


136 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


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L919]  i  mat:   Mutation  in  Matth  L37 

respects,  and  via  versa.  Under  favorable  conditions  this  type  may 
closely  resemble  Snowflake,  but  is  decidedly  more  slender  in  stems, 
leaves,  and  pedicels.  A  characteristic  drooping  of  flowers  and  branches 
is  well  show ii  by  two  plants  in  figure  18;  the  single  is  25b  of  the 
(allies.  The  progeny  of  25b  shown  in  figure  L9  illustrate  a  variability 
of  the  "slender"  characterisl ies  which  has  suggested  the  presence  of 
genetic  differences  among  plants  classed  as  slender.  The  leaves  often 
resemble  those  of  crenate  more  closely  than  do  Snowflake  leaves. 

In  the  field  at  Ithaca  flowering  was  markedly  earlier  than  with 
Snowflake,  and  the  type  seems  to  be  earlier  on  the  whole.  The  River- 
side conditions  have  commonly  given  a  decided  dwarfing  as  compared 
with  Snowflake,  though  not  to  the  extreme  degree  that  this  has  occurred 
with  eremite  (figs.  20  and  21). 

The  results  of  selfing  tests  are  reported  in  tables  34  and  35.  The 
distributions  have  the  same  general  characteristics  as  with  crenate, 
with  some  remarkable  differences.  The  excess  of  doubles  with  Snow- 
flake  is  very  much  greater,  the  ratio  being  about  30:1;  with  slender, 
however,  the  excess  of  singles  is  slight  in  the  grand  total  and  perhaps 
significantly  variable  with  different  parents. 

Plant  25b— 11 ,  the  "extreme"  individual  of  figure  If),  appears  to 
give  a  real  excess  of  slender  over  Snowflake,  and  of  double  slender 
over  single  slender,  though  the  numbers  are  much  too  small  for  cer- 
tainty. The  two  parents  classed  as  "extreme"  are  (tables  39  and  40) 21 
quite  probably  genetically  different  from  the  other  slender  parents. 
Tt  should  be  noted  that  plant  25b-6-8-6,  progeny  of  one  of  the  parents 
described  as  "extreme."  has  also  given  a  relatively  high  proportion  of 
slender  progeny.  Perhaps  the  "extreme"  form  is  heterozygous  for  a 
second  slenderness  factor  similar  to  the  original  one. 

The  percentages  of  mutant-type  progeny  are  (table  39)  much  more 
variable  than  with  smooth,  large,  or  crenate,  and  (table  40)  there  is 
no  good  evidence  of  selective  elimination;  both  these  facts  may  depend 
on  genetic  differences  among  the  parents  tested. 

The  great  modifiability  of  the  various  types,  including  Snowflake. 
indicated  by  a  comparison  of,  for  instance,  figures  14,  15,  and  16. 
greatly  complicates  the  positive  determination  of  types.  Tn  the  cul- 
tures of  1911II  and  1913,  where  crowing  in  flats  or  aphis  injury  in 
the  Held  interfered  with  normal  development  of  some  plants,  the  im- 
pression was  obtained  that  the  slender  type  occurred  in  several  grades 


-i  In  the  calculation  of  the  probability  of  simple  sampling,  f  is  taken  as  3 
(the  number  of  cultures),  not  2  (the  number  of  parents). 


138 


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1919  |  I    ••-.'  •    \Iutai in   Matthiola  139 

probablj  unlike  genetically.     In  the  L916  cultures,  on  the  other  hand, 

with  better  develop at,  this  type  seemed  substantially  as  uniform 

■•is  the  others 

1 1'  we  ignore  Mies,-  possible  genetic  differences  and  attempl  to 
;i|>|)ly  the  scheme  worked  oul  for  crenate,  difficulties  appear  a1  once. 
First,  the  scarcity  of  Snowflake  singles  would  indicate  much  closer 
Linkage  than  with  crenate,  while  the  relative  abundance  of  slender 
doubles  apparentlj  contradicts  this  supposition.  Second,  the  in- 
adequate results  from  crossing  with  Snowflake  (table  :i(>)  surest 
that  the  sperms  carrj  the  supposedly  crossover  slender  factor  al  leasl 
as  often  as  do  the  eggs.  While  crenate  as  pollen  parent  gives  results 
agreeing  tolerably  with  the  hypothesis,  slender  gives  results  differing 
from  these  in  the  w  rrong  direction. 

No  .Ion  I  it.  however,  the  disagreements  can  be  over  emphasized.  Both 
crenate  and  slender  as  seed  parent  seem  to  give  the  expected  relations 
between  singles  and  doubles,  and  series  '-,;!  also  does  this  with  the 
Snowflake  progeny.  Obviously  the  functional  sperms  and  eggs  of  these 
mutant-type  parents  exhibit  different  ratios  between  types,  and  the 
peculiar  results  in  other  respects  with  slender  may  be  related  to  the 
addeil  complication  suggested  above.  The  astonishing  feature  of  the 
data,  of  course,  is  the  great  excess  of  single  slender  over  double  slender 
in  series  2'-] — an  excess  which  suggests  an  actual  significant  excess  of 
singles  in  the  totals  of  all  types  given  by  this  cross — while  with  selfed 
slender  there  is  a  great  total  deficiency  of  singles.  We  may  at  least 
feel  confident  that  the  modifications  of  the  single-double  ratio,  with 
this  type  and  with  crenate,  are  due  to  lethal  action  which  also  affects 
the  proportions  of  viable  slender  and  crenate  gametes  or  zygotes. 

If  differential  viability  before  germination  is  an  important  factor 
with  these  types,  very  probably  it  differs  according  as  Snowflake  or 
the  mutant  type  is  the  seed  parent,  and  according  to  the  parental 
environment.  Tn  other  words,  partial  selective  elimination  during 
seed  formation  may  vary  with  the  environment  of  the  embryos,  accord- 
ing as  this  environment  is  affected  by  either  the  genetic  constitution 
or  the  external  environment  of  the  seed  parent.  I'ntil  such  uncer- 
tainties are  eliminated,  we  are  hardly  justified  in  ruling  out,  for 
the  types  discussed,  the  probability  that  regular  segregation  and  (in 
the  last  two  cases*  true  linkage  are  concerned  in  these  phenomena.  In 
fact,  the  definite  differences  in  ratios  between  reciprocal  crosses  and 
between  at  least  one  of  the  crosses  and  selling  encourage  further 
attempts  at  satisfactory  factorial  analysis. 


140  University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 


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Mutation  in  MatthioJa 


1  II 


6.  THE  \  \i;i;>  >w  i.i:  \vi:i»  TYPE 

As  table  37  indicates,  this  type  c petes  with  crenate  for  second 

place  in  frequency  of  occurrence  in  the  [thaca  cultures;  in  fact,  when 
only  the  Btrictly  unselected  cultures  are  considered  the  percentage  is 
very  close  to  thai  for  smooth-leaved.  A  feature  of  special  interesl  is 
the  apparenl  association  of  the  mutanl  type  with  doubleness. 

In  ;i  cool  greenhouse  this  type  (fig.  22)  varied  from  exceptionally 
late  and  many-noded  to  ordinary  in  both  characters.  The  leaves  (see 
also  6g.  L8)  were  typically  narrow,  rather  strictly  entire,  often  rolled 
backward    or    twisted,    and    typically    more    ascending    than    those    of 

Table  37 

Narrow  leaved  type.    Numbers  of  appart  nt  mutants  and  association  of  the  type 

with  doublt  ness  of  flout  rs. 


Progeny  of  Snowflake  and  early  parents 

Culture 

Total 
examined11 

Narrow-leaved 

Single 

Double 

All 

Cocffieient  of 
mutation 

I'M  Is 

L910 

11*11 1".  house-sown 

A.1!  above 

All  ini-i'lic.  ,| 

725b 
338 
2072 
3135 

•_•  1 1  ( I 

0 

1 

7 
8 
8 

2 

4 

12 

18 
16 

2 
6 

20 
28 
26 

.28  ±    .26 

1.78  ±    .38 

.97   *    .15 

.89  *    .12 

1.08  ±    .14 

*  See  note  b  to  table  2. 
b  See  note  C  to  table  1. 


Snowflake.  The  apex  of  the  leaf  is  often  more  acute  than  with  Snow- 
flake,  and  many  leaves  are  mucronate  or  at  least  end  in  a  sharp,  rigid 
tip. 

A  striking  characteristic  is  the  narrowness  of  the  sepals,  resulting 
in  frequent  early  separation  at  the  edges,  partially  exposing  the  petals 
in    immature   buds. 

Under  the  less  favorable  field  conditions  the  plants  often  remain 
long  as  dwarf  rosettes,  and  flower  late  and  feebly  if  at  all.  Figures  2:5 
and  24  show  comparatively  well  developed  plants  in  the  field. 

The  type  is  on  the  whole  very  distinct  in  the  field,  though  there 
has  been  some  question  whether  a  greenhouse  plant  such  as  thai  in 
figure  18  is  genetically  different  from  those  with  short  and  rigid 
leaves  'figs.  22  and  24);  the  very  great  variability  in  leaf  form  due 
to  external  conditions  makes  such  a  question  very  difficult  without 
extensive  progeny  tests.  It  is  now  (1918)  probable  that  narrow-dark 
(p.  143)  was  not  distinguished  from  narrow  in  the  greenhouse. 


142 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 


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The  i'i'w  singles  have  produced  Few  seeds,  and  these  were  highly 
variable  in  size  The  capsule  often  has  a  defective  septum,  more  or  less 
of  the  distal  portion  being  absent.  Germination  was  poor  in  the  small 
cultures  secured  (table  38,  upper  pari  .  with  only  10.8  per  cenl  of  the 
tnutanl  t.\  pe  among  the  progeny. 

This  case  agrees  in  mosl   respects  with  those  previously  discussed, 

but  adds  one  poinl  of  interesl  in  th currence  of  appareul  coupling 

of  mutanl  type  with  doubleness  rather  than  singleness.  Seed  appears 
to  be  less  abundant  and  less  well  developed  than  with  any  of  the  pre- 
ceding mutanl  types,  facts  probably  significant  in  relation  to  the  low 
percentage  of  narrow  progeny  from  narrow  parents,  though  the  large 
probable  error  of  the  percentage  must  lie  considered. 

7.  MISCELLANEOUS  A.BEBEANT  TYPES 

As  pari  of  the  aberrant  individuals  occurring  in  the  greenhouse 
were  cither  doubles  or  singles  that  produced  no  seed,  while  practically 
no  seed  was  produced  by  any  plants  in  the  field  at  Ethaca  or  by  even 
some  of  the  commoner  mutant  types  at  Riverside  the  opportunity  for 
progeny  tests  lias  been  almost  entirely  limited  to  the  types  SO  far 
discussed. 

The  narrow-dark-leaved  type  (table  3)  was  common  and  distinct 
in  the  field  at  Ithaca,  where  it  constituted  about  .48  per  cent  of  the 
2072  plants  from  house-sown  seed,  and  has  been  readily  identified 
in  several  cases  at  Riverside.  It  was  not  distinguished  in  the  green 
house  cultures,  but  was  very  probably  included  under  narrow-leaved. 
Possibly  a  single  described  as  "small-convexdeaved"  belonged  to  this 
type,  though  two  Geld  plants  were  given  this  name  as  distinct  from 
narrow-dark;  according  to  a  photograph  (fig.  25,  second  plant  from 
left),  another  greenhouse  plant  (a  double)  may  have  been  similar  to 
narrow-dark-leaved.  The  narrow-dark-leaved  type  (figs.  26  and  27) 
has  narrow  dark-green  leaves,  strongly  convex  upward,  and  evidently 
tends  to  compactness  of  growth  and  lateness  of  flowering;  under  field 
conditions  it  seems  decidedly  more  like  Snowflake  than  like  narrow- 
leaved. 

The  44  progeny  (table  38)  secured  from  the  greenhouse  single 
mentionad  above  included  2  (4)  narrow-dark-leaved  individuals  and 
'■\  (5)  other  plants  not  Snowflake  (the  last  including  two  smooth,  one 
large,  one  slender,  and  one  semicrenate),  besides  five  undetermined 
plants.    Plainly  flic  type  of  the  parent  is  still  in  doubt. 


144  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

Another  very  different  greenhouse  plant,  described  as  "stout 
dwarf"  (fig.  25,  third  from  left),  gave  among  29  progeny  (table  38) 
5  (7)  individuals  evidently  not  Snowflake,  which  may  have  been 
narrow-dark  or  may  have  belonged  to  another  type  that  was  somewhat 
similar  under  the  conditions  of  the  tests.  The  parent  resembled 
Snowflake  except  in  its  short  internodes  and  short,  stout  capsules. 

Four  other  plants  suspected  of  mutation  apparently  entirely  failed 
to  repeat  their  type  in  their  progeny,  perhaps  because  of  the  smallness 
of  the  house  cultures.  One  of  these  was  the  plant,  much  branched 
for  the  warm  greenhouse,  third  from  the  right  in  figure  18 ;  another 
was  a  very  late  plant  with  a  remarkably  large  number  of  main-stem 
leaves;  the  others  were  a  plant  with  unusually  small  flowers  and  one 
with  some  of  the  leaves  somewhat  spatulate.  Possibly  all  of  these  were 
Snowflake,  though  the  second,  which  gave  poor  germination,  probably 
was  not.  All  these  four  plants  have  been  included  as  Snowflake 
parents  for  tables  showing  numbers  of  apparent  mutants. 

The  small-smooth-leaved  type  is  well  shown  in  figure  25  (first  and 
fifth  from  the  left) .  It  is  the  smallest  and  weakest  of  the  fairly  common 
and  definitely  identified  types ;  it  has  small,  very  smooth  leaves,  and  is 
late  in  blooming.  The  two  plants  shown  were  both  singles,  but  they 
set  no  seed. 

The* semicrenate-leaved  type  (table  3)  differed  slightly  but  appar- 
ently definitely  from  Snowflake,  somewhat  resembling  crenate-leaved 
in  leaf  form.  The  one  "pointed-crenate-leaved"  plant  of  table  3  may 
have  been  crenate-leaved.  The  "compact"  and  "curly-leaved"  plants 
of  this  table  have  not  been  identified  with  any  aberrant  types  in  other 
cultures.  With  the  remaining  six  types  of  table  3  all  the  individuals 
have  been  questioned  as  possibly  Snowflake ;  it  is  now  practically  cer- 
tain that  some  of  those  in  the  second,  third,  and  fourth  groups 
belonged  to  the  large-leaved  type  since  studied,  but  the  apparent  inter- 
gradation  with  Snowflake  makes  any  attempt  at  a  definite  reclassi- 
fication from  the  records  a  matter  of  doubtful  value. 

The  second  plant  from  the  right  in  figure  25  was  remarkable  for 
its  short  stem  and  few  but  large  leaves.  Several  other  more  or  less 
exceptional  individuals  have  appeared  in  the  cultures,  especially  among 
some  plants  with  abnormal  cotyledons,  selected  from  large  numbers  of 
greenhouse  seedlings  in  the  1908  cultures,  which  were  examined  for 
syncotyledony.  Some  of  these  were  very  weak  plants  which  finally 
died  without  flowering. 


L919]  -' :    Mutation  in  Matthiola  I  15 

The  fluctuations  in  habit,  Leaf  Form,  etc.,  within  the  type  are  such 
thai  the  determination  of  familiar  types  is  often  a  matter  of  some 
uncertainty,  as  is  shown  by  data  thai  have  been  presented.  It  maj 
well  be  thai  among  the  doubtful  types  are  included  several  definite  bu1 
comparative  rare  mutanl  tonus,  which  occurred  too  infrequently  to 
afford  adequate  material   for  positive  classification. 


v   S.iMK   1'Koi:  \l:||.|TES  OF  RANDOM  SAMPLING 

For  compactness  of  presentation  and  convenience  of  comparison 
the  materia]  in  tallies  39  and  40.  to  winch  some  incidental  references 
have  already  been  made,  is  collected  heri'  rather  than  scattered  through 
the  discussions  of  the  various  types  concerned.  Some  statements  as 
to  methods  are  also  necessary  in  connection  with  each  of  the  topics 
here  treated. 

First,  it  should  be  noted  that  the  percentages  previously  given 
have  regularly  been  accompanied  by  the  probable  errors  of  simple 
sampling.    These  probable  errors  have  been  calculated  by  the  formula 

E  per  cent  =  .6744898    \23l   .   where  p   is  the   percentage  of  the  mutant 

n 
type    "successes"),  q  is  1 — p,  and  n  is  the  size  of  the  sample  (the 

cumber  of  plants  concerned). 

In  the  heredity  tables  for  each  type,  p  has  uniformly  been  taken 
as  the  percentage  of  the  total  of  the  lots  compared,  or  p0. 

For  the  "mutation  coefficient"  the  percentage  of  the  grand  total 
of  unselected  house  sown  lots  has  regularly  been  used.  Evidently  the 
few  selected  progeny  included  in  tables  1,  28.  and  37  should  be  omitted. 
All  the  percentages  here  an;  so  low  that  the  probable  errors  deserve 
little  confidence,  even  though  n  is  usually  fairly  large.  The  rather 
dose  agreement  of  the  percentages  of  all  apparent  mutants  in  the 
three  distinct  lots  of  unselected  house-sown  cultures  suggests  that 
they  represent  fairly  well  the  population  value  for  the  potentialities 
of  the  seeds;  and  even  if  the  mean  percentage  of  the  total  of  the  lots 
for  the  main  comparisons  is  actually  nearer,  it  is  safer  to  use  the 
larger  probable  errors  resulting  from  the  method  here  employed. 
Furthermore  strict  use  of  p0  would  sometimes  require  several  slightly 
ditl'ereni  probable  errors  for  the  same  percentage,  for  use  in  different 
comparisons  in  the  same  table. 


146 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 


If  the  probable  error  of  the  difference  of  any  two  percentages  in 
the  same  table  is  to  be  obtained,  therefore,  formulae  corresponding  to 
those  given  by  Yule  (1911,  pp.  264-267)  are  applicable. 

Now,  it  is  possible  in  some  of  these  cases  to  calculate  the  actual 
standard  deviation  of  the  percentage  in  subsamples  which  make  up 
an  aggregate  sample.  Table  39  gives  such  actual  standard  deviations, 
in  comparison  with  the  corresponding  theoretical  or  expected  standard 
deviations  given  by  . 

v  per  rent  ^>  — • 


Table  39 
Standard  deviations  of  percentages  of  mutant  types.     Values  derived  from 
compared  with  values  expressing  the  actual  variability  of  subsamples. 


pq, 


N 

/ 

n 

V 

Standard  deviation  of  samples 

of  mean  size  n 

Type  of  parent  and  grouping  of 
progeny 

Actual 

Theoretical.J-^-*- 
n  -3 

Difference 
Ea- 

Smooth-leaved  type: 
All  lots  by  parentage 
All  lots  as  grown 

234 
234 

6 
12 

39.0 
19.5 

27.35 
27 .  35 

7.5 
11.3 

7.4    ± 

11.0   ± 

1.4 
1.5 

+      .1 

+      .2 

Germination  good 

187 

7 

26.7 

29.95 

10.9 

/    9.4   ± 
I    9.2a 

1.7 

+      .9 

Germination  poor 

47 

5 

9.4 

17.02 

5.2 

114.9   ± 
\17.6 

3.2 

-  3.0 

Large-leaved  type: 
All  lots  by  parentage 
All  lots  as  grown 

357 
357 

20 
22 

17.85 
16.2 

49.02 
49.02 

10.7 
10.9 

13.0  ± 

13.7  ± 

1.4 
1.4 

-  1.6 

-  2.0 

Germination  good 

260 

14 

18.6 

50.38 

11.3 

/  12.7  ± 
I  12.7 

1.6 

-      .9 

Germination  poor 

97 

8 

12.1 

45.36 

8.7 

f 16.5   ± 
\16.6 

2.8 

-  2.8 

Crenate-leaved  type: 
All  lots  by  parentage 
All  lots  as  grown 

633 
633 

20 

28 

31.65 
22.6 

29.86 
29.86 

10.6 
12.5 

8.6   ± 
10.3   ± 

.9 
.9 

+  2.2 
+  2.4 

Germination  good 

549 

20 

27 .  45 

32.42 

10.7 

(    9.5   ± 

\    9.3 

1.0 

+   1.2 

Germination  poor 

84 

8 

10.5 

13.10 

10.5 

f 12 . 3   ± 
116.7 

2.1 

-      .9 

Seed-size  test,  smaller  seeds 

73 

5 

14.6 

65.  ?5 

13.2 

f 13.9   ± 
1 13 . 8 

3.0 

-      .2 

Same,  larger  seeds 

193 

5 

38.6 

20.21 

9.4 

f    6.7   ± 

\    7.9 

1  4 

+   1.9 

Same,  all  seeds,  by  parentage 
Same,  all  seeds,  as  grown 
Slender  type: 

All  lots  by  parentage 
All  lots  as  grown 

Germination  good 

266 
266 

243 
243 

165 

5 
10 

8 
13 

7 

53.2 
26.6 

30.4 

18.7 

23 . 6 

32.71 
32.71 

32.51 
32.51 

33.33 

10.3 
22.9 

17.5 
19.7 

14.9 

6.6  ± 

9.7  ± 

9.0   ± 
11.8   ± 
f 10.4   ± 
1  10.3 

1.4 
1.5 

1.5 
1.6 
1.9 

+  2.6 

+  8.8 

+  5.7 
+  4.9 

+  2.4 

Germination  poor 

78 

6 

13  0 

30.77 

27.2 

f  14  6   ± 
\  14.8 

2.8 

+  4.5 

Parents  "extreme" 

38 

3 

12  7 

63  16 

14.4 

J  15 . 5   ± 
115.1 

4.3 

-     .3 

Parents  ' '  ordinary 

Narrow-leaved  type: 
All  lots  as  grown 

205 
37 

10 
3 

20.5 

12.3 

26.83 
10.81 

14.7 
8.1 

J  10.6   ± 
111. 2 

10.2   ± 

1.6 

2.8 

+  2.6 
-      .75 

■  The  second  values  for  some  oases  in  this  column  are  derived  from  p„   (see  text). 


/   ost:    Mutation  in  Matthiola  I  17 

For  example,  table  -~  gives  the  percentage  of  large-leaved  plants 
among  the  ;!~>7  progeny  of  the  20  Large  leaved  parents  as   19.0  1 1.8 

per  cent.      This  probable  error  is  given   by   .6744898    \       .   where 

ft 

p  =  49.0  per  cent,  q  51.0  per  cent,  and  n  357.  These  ::">7 
progeny,  as  table  39  indicates,  came  from  20  parents  which  contributed 
;ni  average  of  17  s".  progenj  each,  and  the  actual  standard  deviation 
of  the  percentage  in  these  20  sibships  was  10.7  per  cent. 

Obviously  the  expected  standard  deviation  of  simple  sampling  Eor 
comparison  must  represenl  samples  ool  of  357  plants  each  l>ut  of  17.85 
plants  each.  Now  a  percentage  is  obviously  a  mean  of  values  all 
eitherOor  l  .  Since  "Student"  (1908)  lias  shown  thai  the  theoretical 
standard  deviation  of  the  mean  in  samples  is  given  more  exactly  by 

"■  vartat.'        ..  1  fvartate 

than   nv  (7, 


y/n  —  3  \  a 

(the  value  Eor  the  normal  curve  conventionally  used  Eor  the  probable 

<']■]■<']■  of  the  mean)   and  since  n,  the  mean  size  of  sample,   is  small 
enough  to  make  t|lt.  direction  a  matter  of  considerable  importance, 

V  n  —  3    is    here    u^t^l.      Since    o-  variate  =  VPrJ-    Wf>    have    o-mcan  = 

y_  P^    .  where  Ti  =  17.8").     This  gives  a  theoretical  standard  devia- 

//  —  3 
tion  of  13".0  per  cent.22 

It  is  true  (Yule,  L911,  p.  260)  thai  the  ordinary  method  of  calcu- 
lation of  the  actual  standard  deviation  is  not  satisfactory  for  means 
when  the  samples  vary  in  size.  A  method  has  been  used,  however,  which 
obviates  this  difficulty,  so  thai  comparison  with  the  results  given  by 

pq         ....  .      . 

is  strictly  legitimate.     Each  squared  percentage  deviation 


£ 


71  —  3 
has  been  weighted   by  multiplying  it   by  the  number  of  individual 

plants  which  it  represents,  and  the  summation  of  squared  deviations 

has  then  Keen  divided,  not  by  2/,  the  number  of  samples,  but  by 
2/ X  7v.  the  number  of  samples  multiplied  by  the  mean  weight  or 
average  size  of  sample  i  in  other  words,  by  A",  the  total  number  of 
individuals  1 .2S 


--  In  the  calculations  for  table  39  p  has  been  taken  as  the  percentage  given 
in  this  table,  to  two  decimal  places,  while  with  all  other  numbers  employed  in 
calculation,  including  77 — 3,  three  or  more  decimal  places  have  been  used  as 
nee. led. 

Algebraic  proof  of  the  correctness  of  the  method  has  kindly  1 i  furnished 

by  Frank  L.  Griffin,  Professor  of  Mathematics,  Weed  College,  Portland,  Oregon. 
If  it  develops  that  this  rather  obvious  device  has  not  been  suggested  for  the 
purpose,  it  is  to  be  presented  elsewhere  with  the  mathematical  proof.  When  the 
\:niates  are  not  grouped  in  classes  the  calculation  is  substantially  as  easy  as 
without  weighting,  while  the  theoretical  value  is  found  with  much  less  work 
than  by  the  method  given  by  Yule  (1911,  p.  -*50),  which  requires  the  harmonic 
mean  of  the  sample  sizes. 


148 


University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 


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Frost:    Mutation  in   Vatthiola  I  19 

In  the  calculation  the  deviations  are  taken  iVmn  zero,  and  with 
these  small  numbers  of  samples  the  percentages  are  no1  thrown  into 
classes;  it  suffices,  then,  to  square  each  number  of  "successes,"  divide 
bj  the  corresponding  total  of  individuals,  add  the  quotients,  and 
divide  by  the  grand  total  of  individuals,  correcting  this  weighted 
mean  squared  deviation  by  subtracting  the  square  of  the  weighted 
mean  percentage  (percentage  of  grand  total).  If  s  is  the  number 
of  successes  and   n   is  the  total   number  of   individuals   in   the  sub- 

sample,  and  .1/  is  the  weighted  mean  percentage,  then  M=— — ,  and 

It- 

a  per  J-^t  )l  ,  , 

Table  39  gives,  for  the  mosl  important  comparisons  of  heredity 
percentages,  the  total  number  of  progeny  (N)>  the  number  of  cultural 
groups  or  with  the  first  line  for  each  type)  the  number  of  parents  (/), 
the  average  size  of  the  groups  of  progeny  (w),  and  the  mean  per- 
centage  of  the  mutant  type  (p).  This  serves  as  a  summary  of  some 
of  the  must  important  statistical  data  already  presented  relating  to 
the  inheritance  of  these  types,  and  also  shows  the  basis  of  tlie  remain- 
ing pari  of  this  table  and  of  table  40.  For  comparison  of  actual  and 
theoretical  standard  deviations  the  theoretical  value  has  been  calculated 
from  the  actual  percentage  as  given  in  this  table.  For  comparison  of 
means  (table  40)  the  percentage  of  the  corresponding  total  (p0)  has 
also  been  used,  tins  theoretical  standard  deviation  being  the  second  in 
the  table  in  the  cases  where  the  two  values  are  not  identical. 

Since  small  changes  in  a  percentage  have  little  effect  on  its 
theoretical  standard  deviation,  we  are  fairly  well  justified  in  taking 
the  latter,  as  calculated  from  the  actual  percentage  in  each  case,  to  be 
the  "population"  value.  Consequently,  the  difference  between  the 
theoretical  and  actual  standard  deviations  has  been  expressed  in  each 
case  as  a  multiple  of  the  probable  error  of  the  theoretical  value. 

Aside  from  the  last  line  for  crenate-leaved,  where  there  is  an 
obvious  artificial  reason  for  high  variability,  there  is  no  very  significant 
difference  except  with  slender.  In  Ibis  case,  the  deviation  of  5.7  times 
the  probable  error  (line  1)  is  probably  largely  due  to  the  genetic 
differentiation  of  "extreme"  and  "ordinary"  parents  suggested  by 
their  appearance  and  by  the  wide  difference  in  the  heredity  per- 
centages: the  differences  become  moderate  when  the  progeny  of  the 
two  classes  of  parents  are  separated. 


150  University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 

In  the  two  cases  (smooth-leaved  and  crenate-leaved  types)  where 
the  percentages  of  mutant  types  differ  greatly  with  good  and  poor 
germination,  separation  according  to  germination  gives  a  mean  value 
of  the  standard  deviation  decidedly  lower  than  the  value  for  all  lots 
taken  together.  In  the  case  of  the  large-leaved  type  there  is  little 
change,  while  the  considerable  reduction  with  the  slender  type  is 
probably  due  to  unequal  separation  of  lots  from  parents  genetically 
different. 

Table  40  shows  the  simple-sampling  probability  of  the  most  striking 
differences  of  heredity  percentages,  aside  from  the  characteristic 
differences  between  different  types.  "Student's"  (1917)  table  of 
probabilities  of  mean  deviations  with  small  samples  is  used,  with 
interpolation  by  second  differences.  "Where  the  standard  deviation 
of  the  difference  is  required  it  is  found  from  the  theoretical  values 
given  in  table  39  by  the  formula  (Yule.  1911,  pp.  264-265) 


V  difference Vcrl  ~~H  a 


■  J    Ppgo 


Po  Qo 


ny  — ■  3      n2  —  3 

when  one  statistical  population  is  assumed  (table  40,  columns  2  and  3). 
When  two  populations  are  assumed  (table  40,  columns  4  and  5)  the  cor- 
responding formula  using  p1q1  and  p2q2  is  employed.  In  the  one  case 
where  this  is  possible  (the  seed-size  test),  it  is  also  calculated  from  the' 
actual  differences  of  the  pairs  of  percentages  in  the  separate  tests,  each 
difference  being  weighted  with  the  total  number  of  progeny  from  the 
parent  concerned.  Where  two  values  of  /  (the  n  of  "Student's" 
table)  are  involved,  the  smaller  is  taken,  giving  understatements  of  the 
probabilities  involved ;  in  the  two  cases  where  the  difference  is  more 
than  2,  the  values  are  recalculated,  with  /  as  the  nearest  smaller 
integer  to  the  geometric  mean  of  the  two  actual  numbers  (that  is 
with  /0  =  V/i/2)-  In  the  case  where  the  probabilities  of  four  devia- 
tions all  in  the  same  direction  are  combined,  the  four  chances  of 
occurrence  are  multiplied  together;  that  is,  if  the  J(l  +  o)  of 
"Student's"  table  is  P,  and  1  —  P  is  F,  then  F1.2.^.^  =  F1-F2-F^Fi. 
"Student"  (1908,  p.  1)  says,  "The  usual  method  of  determining 
the  probability  that  the  mean  of  the  popidation  lies  within  a  given 
distance  of  the  mean  of  the  sample,  is  to  assume  a  normal  distribution 
about  the  mean  of  the  sample  .  .  .  ."  When  this  is  done  with  a  differ- 
ence of  means,  it  is  at  once  evident  that  only  half  of  the  chances  of 
deviations  as  great  as  the  distance  of  the  given  difference  from  zero 
difference  lie  below  zero  difference ;  the  other  half  of  the  chances  of 


1919]  /    oat:    kfutatton  in  Matthiolo  15] 

such  deviations  Lie  in  the  opposite  direction  and  represenl  positive 
differences  still  greater  than  the  sample  difference.  In  other  words, 
it'  the  implications  of  a  sample  difference  are  to  be  given  full  weight, 
this  difference  musl  be  considered  the  most  probabh  valut  of  the 
theoretical  "true"  difference  between  two  assumed  distinct  statistical 
populations.  In  the  presenl  case  we  wish  to  know  the  probability  thai 
the  "true"  or  theoretical  population  means  differ  in  the  same  srn.sc 
as  the  observed  sample  means.  Tliis  involves  calculation  of  the  proba 
bility  of  deviations  in  one  direction  (beyond  zero  difference)  from 
the  .sample  difference.  It'  the  sample  difference  of  means  is  considered 
as  positive,   then   the   negative  "tail"  of  the  theoretical    frequencj 

curve  of  sample  differe IS   I  this  curve  he  in.".'  centered  at   thi'  observed 

sample  difference)  must  be  compared  with  the  rest  of  the  curve.  The 
positive  portion  of  the  curve  the  \  (1  +a)"4  of  the  tables,  then  gives 
the  chances  favoring  the  hypothesis  that  the  sample  means  truly 
Pi  presenl  the  population  means.  The  odds  in  favor  of  the  hypothesis 
are  therefore  <_ii\  en  bj    t  he  formula 

0  =*(!  +  «>    or  i±li 

u*     i(i  — «)  01  J  — K 

Values  calculated  from  this  formula  are  given  in  columns  4  and  .">  of 
table  40. 

When  other  considerate  as  than  the  sample  evidence  arc  to  be  taken 
as  determinirig  the  most  probable  value  of  the  "true"  mean,  the  ease 
is  different.  For  example,  if  the  probability  that  our  sample  per- 
centages  are  mere  sampling  deviations  from  some  theoretical  Mendelian 
value  were  in  question,  that  theoretical  value  must  be  taken  as  the 
population  mean  and  only  the  magnitude  of  the  deviations  must  be 
considered. 

When  ,-i  difference  of  means  is  considered  from  this  latter  stand- 
point, it  is  assumed  that,  the  two  samples  come  from  one  statistical 
population,  and  hence  that  zero  is  the  most  probable  value  of  the 
population  difference.  If  we  choose  to  assume  that  the  most  probable 
value  of  the  population  difference  in  our  cases  is  zero,  we  must 
calculate  the  odds  against  a  deviation  of  the  observed  amount  in 
either  direction    from  zero  difference.     The  formula    for  these  odds  is 


2X{(1-  a)  1  —  a 


-■>  The  whole  area  of  the  frequency  curve  is  taken  as  unity,  ami  a  is  the  area 
enclosed  by  any  given  deviation  in  both  directions  from  the  mean. 


152  University  of  California  Publications  in  Agricultural  Sciences       \  Vol.  4 

Values  from  this  formula  are  given  in  columns  2  and  3  of  table  40; 
their  magnitude  in  three  cases,  however,  and  the  uniform  agreement 
of  the  direction  of  difference  with  the  expectation  from  biological 
evidence  which  has  been  discussed,  weigh  heavily  in  each  test  against 
the  assumption  of  random  sampling  from  a  single  statistical  population. 

It  does  not  appear  necessary,  however,  thus  to  weigh  the  evidence 
in  detail  before  deciding  which  formula  is  suited  to  the  case.  There 
is  no  evident  theoretical  value  from  which  these  percentages  are 
reasonably  likely  to  be  sampling  deviations.  This  being  the  case,  and 
granting  such  general  possibilities  as  that  of  differential  viability,  it 
seems  most  reasonable  to  use  the  former  (0X)  formula.  That  is,  we 
should  give  full  weight  to  the  implications  of  a  sample  deviation 
unless  there  is  some  definite  reason  for  assuming  that  some  other  value 
better  represents  the  mean  of  the  theoretical  statistical  population. 

It  must  be  remembered  that  the  actual  probabilities  of  sampling 
deviations  do  not  necessarily  correspond  closely  with  the  probabilities 
of  random,  sampling.  With  the  material  in  table  40,  however,  aside 
from  the  germination  comparison  in  the  case  of  the  slender  type, 
table  39  suggests  a  fair  agreement  with  the  conditions  of  random 
sampling.  The  actual  standard  deviations  of  the  subsamples  do  not 
in  general  differ  widely  from  the  corresponding  theoretical  values,  and 
the  differences  are  negative  about  as  often  as  positive. 

The  hypothesis  of  selective  elimination  with  poor  germination  is 
strongly  sustained  (table  40),  although  only  one  difference  (with  the 
crenate  type)  has  much  statistical  significance  when  considered  alone. 
If  we  may  multiply  together  the  members  of  the  four  ratios  in  column 
3  of  the  table,  the  combined  odds  (using  the  /„  values)  are  130:1 
against  occurrence  of  these  four  deviations  as  accidents  of  simple 
sampling,  when  magnitude  of  deviation  alone  is  considered.  If 
direction  of  deviation  alone  is  considered  the  random  chance  of  these 
four  deviations  all  in  the  same  direction  is  obviously  (-J)4,  or  the  odds 
favoring  the  elimination  hypothesis  are  15:1.  Combination  of  these 
two  chances  indicates  a  high  probability  for  the  hypothesis.  When 
the  two-population  formula  is  used  in  calculating  the  standard  devia- 
tion of  the  difference  (columns  4  and  5)  the  value  of  P  is  consider- 
ably reduced  in  some  cases,  and  the  combined  odds  obtained  from 
Fx  ■  F.,  •  -F3  ■  F4  are  very  high.  Evidently  the  best  single  expression 
of  the  simple-sampling  odds,  though  possibly  somewhat  too  high,  is  the 
value  given  last  in  column  5,  or  123,093:1. 

With  the  seed-size  test  of  crenate  the  odds  are  499 : 1  with  the 
theoretical  standard  deviation  of  the  difference,  or  1666 : 1  with  the 


1919J  /  roat:   Mutation  vn  Matthiola  ]•">•'! 

actual  standard  deviation.  When  the  relativelj  small  size  and  weals 
growth  of  erenate  seedlings  are  also  taken  into  account,  the  relatively 
small  average  size  of  erenate  embryos  may  be  considered  to  be 
demonstrated  beyond  reasonable  doubt. 

With   "extreme"  and  "ordinary"  slender  parents  the  odds  de 
cide'dly  favor  the  hypothesis  of  genetic  differentiation  of  parents,  in 
spite  of  ilif  small  numbers  involved.    We  must  remember  thai  definite 
statistical  differentiation  of  lots  of  progeny  grown  under  uniform  con 

ditions  does  uo1  necessarily  demonstrate  gt  >tt  tie  differei s    differences 

in  outpul  of  gametes  between  the  parents;  in  this  case,  however,  the 
difference  in  the  appearance  of  the  parents  and  in  the  single-double 
ratio  ; ing  the  progem    also  surest   genetic  differentiation. 


GE  X  K  UAL  1  )ISCUSSIOXL'"' 

It  might  be  argued  with  some  plausibility  that  the  available 
evidence  hardly  justifies  conventional  factorial  analysis,  or  at  least  that 
the  data  indicate  strongly  the  presence  of  marked  factorial  incon- 
stancy. The  aberrant  types  occur  in  very  small  proportions  among 
the  progeny  of  selfed  Snowflake  parents,  in  much  larger  proportions 
from  "mutant-type*'  parents,  and  in  intermediate  proportions  from 
crosses  with  Snowflake.  It  might  he  supposed  that  the  Snowflake  type 
has  a  slight  tendency  to  mutate  to  the  other  types,  and  that  these  have 
a  much  mure  marked  tendency  to  mutate  hack  to  Snowflake.  Various 
considerations,  however,  especially  the  occurrence  of  apparently 
regular  linkage  phenomena,  seem  to  favor  the  general  form  of 
hypothesis  which  has  been  presented. 

As  we  have  seen,  it  is  well  known  from  the  behavior  of  various 
factors  that  the  typical  Mendelian  mechanism  is  present  in  Matthiola. 
It  cannol  be  argued  here,  as  sometimes  with  Oenothera,  thai  the 
genetic  behavior  of  the  genus  or  species  is  fundamentally  non- 
Mendelian.  Since  the  .Mendelian  mechanism  is  demonstrably  present, 
and  .Midler's  1918)  work  on  beaded  wings  in  Drosophila  seems  to 
establish  the  adequacy  of  this  mechanism  in  a  closely  parallel  ease. 
surely  conventional  factorial  analysis  should  be  carried  as  far  as  pos- 
sible; in  fact  i  .Mu Her.  1018,  p.  42:?),  a  .Mendelian  explanation  should 
not  be  abandoned  for  anything  short  of  positively  contradictory 
evidence. 


-'Mutter's  (1918)   complete  report  on   the  beaded-wing  case   in   Drosophila 

appeared  several  months  after  the  present  paper  had  gone  to  the  publisher. 
Certain  conclusions  given  below,  very  similar  to  Muller's  but  not  credited  to 
him,  were  therefore   reached    independently. 


154  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

In  the  Drosophila  case  just  mentioned,  the  "principal"  factor  for 
the  character  in  question  is  "dominant  for  its  visible  effect  and 
recessive  for  a  lethal  effect,"  so  that  no  pure  beaded  individuals 
appear  among  the  progeny  of  beaded.  The  original  race  regularly 
gave  progeny  partly  heterozygous  beaded  and  partly  homozygous 
normal,  while  after  a  long  period  of  selection  a  true-breeding  beaded 
race  appeared.  This  latter  form,  it  proved,  fails  to  give  normals  not 
because  of  being  duplex  for  beaded — it  is  still  simplex — but  because 
of  its  possession  of  another  factor,  known  only  by  its  lethal  effect 
when  homozygous,  which  is  carried  by  the  chromosome  bearing  the 
normal  allelomorph  of  the  factor  for  beaded.  The  locus  of  this  reces- 
sive lethal  factor  gives  in  general  about  10  per  cent  of  crossovers  with 
the  locus  of  beaded,  but  in  this  case,  because  of  the  presence  of  a  factor 
"which  almost  entirely  prevents  crossing  over"  between  the  loci  of 
the  two  lethal  factors,  viable  non-beaded  zygotes  are  very  rarely 
produced.  Thus  every  zygote  receiving  either  two  beaded-carrying 
chromosomes  or  two  non-beaded-carrying  chromosomes  of  the  pair 
concerned  fails  to  develop,  and  all  the  insects  produced  are  necessarily 
heterozygous  for  both  lethal  factors. 

A  point  of  special  interest  in  this  case  is  the  fact  that  by  certain 
crosses  individuals  can  be  produced  which  give  certain  types  among 
their  progeny  in  very  small  percentages.  Muller  suggests  that  part 
at  least  of  the  supposed  mutants  of  Oenothera  may  be  due  to  crossing 
over  between  chromosomes  carrying  lethal  factors,  by  which  certain 
recessive  factors  are  permitted  to  come  to  expression  in  viable  zygotes. 

For  the  inheritance  of  doubleness  of  flowers  in  Matthiola  he  gives 
a  "balanced-factor"  explanation  essentially  identical  with  mine  (Frost, 
1915). 

There  seems  to  be  little  reason  to  doubt  that  the  differential  factors 
for  these  aberrant  Matthiola  types  have  originated  by  mutation.  On 
the  analogy  of  Drosophila  we  might  expect  that  the  true  mutations 
would  be  relatively  rare,  and  that  most  of  the  apparent  mutants,  in 
cases  where  they  appear  frequently,  would  be  due  to  segregation, 
appearing  as  the  result  of  crossing  over  in  chromosomes  carrying 
balanced  lethal  factors.  The  evidence  seems  to  indicate,  however,  that 
the  differential  factors  for  the  mutant  types  at  all  extensively  studied 
are  dominant  for  their  visible  effects  and  usually  (probably  imper- 
fectly) recessive  for  a  lethal  effect,  the  mutant  factors  thus  being 
genetically  similar  to  the  factor  for  beaded  wings  in  Drosophila. 
This  would  seem  to  imply  the  occurrence  of  certain  mutations  in  pro- 


1919]  /  roat:    Mutation  in  Matthiola  L5S 

portions  ;is  high  as  aboul  1  per  cent,  and  a  general  mutation  eoefficienl 
of  perhaps  1.5  per  cent,  while  the  onlj  Mendelian  alternative  would 
seem  to  be  some  more  complex  scheme  whose  satisfactory  formulation 
mighl  require  much  more  extensive  hybridization  data. 

To  be  more  specific :  (1)  these  tj  pes  are  do1  single  recessives,  since 
they  are  ool  homozygous  bu1  split  into  the  mutanl  and  "normal" 
types;  (2)  they  ;ire  nut  simple  cases  of  multiple  recessives,  as  has 
been  proposed  by  Beriberi  Nilsson  (1915)  for  Oenothera  mutations. 
since  what  is  on  thai  hypothesis  the  full  dominanl  t,\  pe  reappears  with 
selfing;  (3)  if  these  types  are  single  dominants,  as  they  appear  to  be, 
they  cannol  (barring  the  action  of  inhibiting  factors)  arise  Erom  the 
pure  recessive  "normal"  or  Snowflake  type  by  segregation,  hut  only 
by  immediate  mutation;  (4)  they  are  not  simple  cases  of  comple- 
mentary dominant  factors,  since  they  occur  among  the  progeny  of 
selfed    parents. 

We  mighl  assume  that  a  "mutant"  type  depends  on  two  pairs  of 
factors,  one  homozygous  and  the  other  heterozygous,  while  both  pairs 
are  heterozygous  in   the  "mutating"  Snowflake  parent.      Thus  the 

d   a 

crenate  type  might  have  the  zygotic  formula  -= -,  where  d  is  the 

Cv  ft 

factor  for  double  flowers,  C  a  dominant  factor  for  crenate,  and  /  a 
dominant   inhibitor  of  C,  all  three  loci  being  situated   in  the  same 

chromosome,  at  distances  of,  say.  16  and  4  units  apart,  in  tl rder 

indicated.      A    Snowflake    parent    producing    crenate    progeny    would 

then  be-: — -  or     ,  — •-.  and  crossover  combinations  would  produce  the 
de%         del 

apparently   mutant    crenate    progeny.      The    crenate    progeny    would 

behave  as  heterozygous  dominants  when  selfed,  and   if  CC  zygotes 

were    non-viable    would    yield    constant    Snowflake    and    inconstant 

crenate;    the    extracted    Snowflake    singles,    having    the    composition 

Dei 

— ;— r,  could  not  throw  en  null  iuiliriilinds  except  bv  true  mutation  of 
dci 

c  to  C.  With  selfed  Snowflake,  if  we  assume  16  per  cent  and  4  per 
cent  of  crossing  over  in  the  two  positions,  and  a  60-per-cent  selective 
elimination  of  crenate  zygotes,  all  CC  zygotes  being  non-viable,  sub- 
stantially the  observed  percentages  of  crenate  singles  and  doubles 
result.'-'" 


26  See  page  125,  footnote.  This  scheme  agrees  fairly  well  with  the  results 
from  crossing,  and  gives  almost  exactly  the  observed  proportion  of  total  doubles 
(a  little  over  53  per  cent)  for  selfed  Snowflake.  Its  adequate  presentation  must 
be  reserved  for  a  later  paper. 


156  University  of  California  Publications  in  Agricultural  Sciences       [Vol.4 

Formerly  (Frost,  1916)  the  hypothesis  of  frequent  dominant 
mutations  seemed  the  more  probable,  but  there  is  apparently  non- 
conformable  evidence.  It  is  true  that  the  peculiar  behavior  of  the 
slender  type  might  conceivably  depend  on  an  occasional  mutation  in 
another  locus,  or  an  exchange  (Shull,  1914)  or  duplication  of  loci, 
giving  two  similar  or  identical  factors  for  slender.  An  apparently 
fatal  objection,  however,  is  the  fact  that  the  supposed  mutants  seem 
to  show  linkage  with  singleness  or  doubleness  at  their  origin  from 
Snowflake  as  well  as  in  subsecpient  generations — a  fact  which  strongly 
suggests  segregation  in  the  former  case. 

If  the  apparent  mutants  are  really  due  to  segregation  complicated 
by  lethal  action,  the  origin  of  the  complex  heterozygosis  indicated  for 
Snowflake  is  doubtful;  it  may  be  due  to  hybridization,  but  more 
probably  to  a  gradual  accumulation  of  mutant  factors  in  balanced- 
lethal  combinations.  On  the  analogy  of  Midler's  Drosophila  case, 
especially,  it  might  be  expected  that  the  latter  would  be  the  true 
explanation,  particularly  since  self  fertilization  seems  to  be  the  rule 
in  Matthiola.  On  this  basis  the  term  mutant  type  is  used  with  some 
confidence  in  this  paper,  while  the  aberrant  individuals  have  been 
called  apparent  mutants. 

We  must  not  forget  that  some  of  the  mutant  types  may  arise,  as 
with  Oenothera  gigas  and  0.  lata,  by  non-disjunction,  or  reduplication 
of  chromosomes,  and  that  this  fact  may  determine  their  heredity. 
This  is  not  to  be  expected  with  the  types  whose  factors  show  apparent 
coupling  with  singleness  or  doubleness.  but  it  might  be  true  of  the 
apparently  unlinked  smooth-leaved  type.  A  preliminary  study  of 
several  types  shows  that  the  usual  somatic  number  of  chromosomes 
is  probably  fourteen,  but  that  positive  counts  are  difficult.  AVhile  it 
might  be  very  hard  to  demonstrate  the  regular  presence  of  one  extra 
chromosome  in  an  individual  or  a  type,  it  should  be  easy  to  decide 
between  the  diploid  and  triploid  numbers.  The  large-leaved  type  is 
so  strongly  suggestive  of  0.  gigas  that  it  would  not  be  surprising  to 
find  the  triploid  number  in  the  material  now  on  hand  for  examination. 

In  a  preliminary  paper  on  these  types  the  writer  (Frost,  1916) 
discussed  some  possible  relations  of  mutation,  heterozygosis,  and 
partial  sterility,  with  special  reference  to  Oenothera,  mentioning  the 
possibility  that  special  prevalence  of  heterozygosis  in  the  genus  may 
be,  "in  large  part,  a  result  rather  than  a  cause  of  mutation."  This 
suggestion  is  evidently  justified  even  if  much  of  the  supposed  mutation 
of  Oenothera  is  really  segregation,  since  it   is  highly  probable  that 


1919  i  /   osi :    Mutation  in  Matthiola  1">7 

the  peculiar  phenomena  depend  on  Lethal  factors  or  combinations  of 
factors  originally  due  to  tnutal  ion. 

Another  possibility  there  mentioned,  advanced  by  Belling  (1914) 
and  since  specially  discussed  by  Goodspeed  and  Clausen  (1917),  is 
thai  of  the  occurrence  of  Lethal  combinations  of  certain  factors  which 
in  other  combinations  may  be  in  no  way  prejudicial  to  normal  develop- 
ment. As  the  latter  paper  shows,  it  is  probable  thai  in  certain 
crosses  between  "good  species"  most  of  the  new  combinations  brought 
together  in  the  formation  of  F,  gametes  are  incompatible  with  the 
production  of  functional  gametes.  Perhaps  in  the  ease  of  Oenothera 
there  may  exist  within  a  species  factors  lethal  in  any  combination 
when  homozygous,  and  other  factors  lethal  only  in  certain  com- 
binal  ions. 

A  balanced-factor  explanation  for  the  inheritance  of  doublcness-7 
in  Matthiola,  a  case  which  Midler  1918)  discusses,  seems  to  have  been 
first  definitely  stated  by  G-oldschmidl  (1913),  though  he  failed  to  pro- 
\  ide  for  one  feature  of  the  evidence,  the  deviation  of  the  heredity 
ratio  from  50  per  cent.  As  has  been  shown  (Frost,  1915),  this 
peculiarity  may  be  due  to  greater  viability  of  the  homozygotes  (sterile 
doubles)  during  embryonic  development,  since  the  doubles  are  more 
viable  in  the  mature  seeds  and  more  vigorous  in  later  development 
Saunders,  1915).  In  this  case  the  "normal"  factor  is  completely 
eliminated  in  favor  of  the  mutant  (sterile-double)  factor  in  the 
formation  of  the  sperms,  and  probably  is  partially  eliminated  in  the 
formation  of  either  the  eggs  or  the  embryos  or  both. 

Here  the  normal  singleness  (sporophyll)  factor  D  may  act  as  a 
lethal  in  the  heterozygous  parent,  possibly  from  its  general  relations 
of  growth  vigor  in  the  presence  of  the  more  vigorous  (/-carrying  cells. 
If  the  lethal  factor  is  situated  in  a  distinct  locus,  evidently  crossovers 
are  at  most  extremely  rare.  Tt  is  true  that  Miss  Saunders  (1911) 
finds  that  F,  hybrids  with  pure  single  forms  produce  functional 
single-carrying  pollen;  with  the  pure  single  forms  from  which  the 
original  "double-throwing"  mutants  arose,  however,  this  might  not 
be  true,  or  a  lethal  change  may  have  occurred  in  the  singleness  factor 
itself  rather  than  in  a  factor  coupled  with  it.  The  Drosophila  case 
would  suggest  a  lethal  change  in  another  locus  of  the  single-carrying 
chromosome. 

In  my  paper  of  1915  this  lethal  change  in  one  chromosome  ap- 
parently accompanying  the  mutation  of  D  to  d  in  the  homologous 


-'  For  a  brief  outline  of  the  genetic  behavior  of  doubleness  see  the  discussion 
of  the  experimental  data  for  the  smooth-leaved  type. 


158  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  4 

chromosome  was  considered  puzzling.  Evidently,  however,  it  may 
have  occurred  in  one  chromosome  before  D  mutated  to  d  in  the  other, 
and  even  then  may  have  produced  its  lethal  effect.  It  is  evident 
that  if  doubleness  should  arise  in  the  absence  of  the  lethal  effect  it 
would  tend  to  be  eliminated  by  the  return  of  one-third  of  the  singles 
to  the  homozygous  condition  in  each  generation.  In  fact,  it  is  possible 
that  the  lethal  change  arose  later  than  doubleness,  as  in  the  Droso- 
j)1iila  case,  or  was  brought  in  later  by  cross  pollination,  and  happened 
to  be  preserved  as  a  result  of  horticultural  selection  for  a  high  pro- 
portion of  doubles. 

A  parallel-column  comparison  between  the  double  type  and  the 
types  especially  discussed  above  has  already  been  given,  in  connec- 
tion with  the  smooth-leaved  type.  It  will  now  be  seen  that  this  com- 
parison seems  to  apply  to  all  mutant  types,  except  early,  that  have 
been  genetically  tested,  the  principal  differences  between  these  types 
relating  to  the  heredity  percentage  and  the  apparent  presence  or 
absence  of  linkage  with  the  single-double  factors. 

From  the  standpoint  of  its  relation  to  genetic  analysis  the  double- 
ness factor  is  remarkably  similar  to  the  sex  factor  in  animals.  There 
are  two  types  in  each  generation,  one  heterozygous  and  the  other 
evidently  homozygous,  and  these  types  are  produced  by  the  fertiliza- 
tion of  two  kinds  of  eggs,  produced  in  equal  or  nearly  equal  numbers, 
by  a  single  kind  of  sperm.  Although  one  of  the  somatic  types  is 
sterile,  and  the  uniformity  of  the  sperms  produced  by  the  other  is  due 
(evidently)  to  lethal  action,  the  opportunity  for  chromosome  analysis 
is  similar  to  that  with  sex  chromosomes. 

We  may  say  that  the  doubleness  factor  and  its  normal  allelomorph 
(d  and  D)  are  carried  by  chromosome  pair  I.  Already  we  know 
several  other  pairs  of  factors  evidently  carried  by  this  pair  of  chromo- 
somes. These  are,  to  name  only  the  mutant  or  possibly  mutant 
member  of  each  pair  of  factors:  P  (pale  sap  color)  and  W  (colorless 
plastids),  both  studied  by  Miss  Saunders  (1911,  1911a)  ;  C  (crenate- 
leaved),  S  (slender;  possibly  two  factors),  and  N  (narrow-leaved). 
As  we  have  seen,  the  last  three  of  these  are  probably  lethal  when 
homozygous,  and  one  or  more  unidentified  lethal  factors  may  be  con- 
cerned in  the  breeding  results,  while  the  doubleness  factor  affects  the 
race  much  like  a  recessive  lethal,  since  all  dd  individuals  are  completely 
sterile. 


Froat:   Mutation  in  Matthiola  LS9 


SUMMARY 

This  paper  describes  the  occurrence,  characteristics,  and  heredity 
of  certain  aberranl  planl  types  which  decidedly  resemble  some  of  the 
"mutant"  types  produced  by  Oenothera  lamarclciana.  The  parent 
Eorm  is  Matthiola  annua  Sweet,  of  the  horticultural  variety  "Snow- 
flake." 

These  aberranl  forms  may  be  called  mutant  types,  since  it  is  highly 
probable  that  they  are  originally  produced  by  mutation.  The  aberranl 
individuals  may  be  termed  apparent  mutants,  since  it  may  be  con- 
sidered uncertain  whether  they  usually  arise  by  immediate  mutation 
or  by  segregation.  The  case  acquires  special  significance  because  indi- 
viduals belonging  to  the  mutant  types,  although  the  species  is  known 
to  be  typically  Mendelian  with  respeel  to  various  characters,  give 
erratic  heredity  ratios  suggestive  of  Oenothera. 

At  least  eight  types  have  been  somewhat  carefully  studied,  and  six 
of  these  have  shown  their  heritability  in  progeny  tests.  Several  other 
types  have  been  named,  but  for  various  reasons  their  distinctness  is 
more  or  less  doubtful. 

Some  of  the  commoner  types  have  each  been  produced  by  many 
parents,  and  in  several  pure  lines  isolated  from  the  original  com- 
mercial variety.  The  apparent  mutants  other  than  the  early  type  com- 
pose about  four  or  live  per  cent  of  the  progeny  of  Snowflake  and  early 
parents,  the  separate  types  ranging  down  from  about  one  per  cent. 

Most  of  the  mutant  types  are  in  general  inferior  to  Snowflake  in 
vigor,  and  the  difference  in  development  is  greatly  increased  by  certain 
unfavorable  environmental  conditions.  The  proportion  of  apparent 
mutants  in  cultures  from  Snowflake  parents  appears  to  be  definitely 
lower  where  germination  is  comparatively  poor. 

The  mutant  types  differ  from  Snowflake  and  from  each  other  in 
various  respects.  The  early  type  is  practically  a  smaller  and  earlier 
Snowflake.  The  other  mutant  types,  on  the  other  hand,  differ  markedly 
from  Snowflake  in  vigor,  fertility,  and  various  form  and  size  char- 
acters. Each  type  is  named  from  some  conspicuous  characteristic 
difference  from  Snowflake,  but  usually  various  other  differences  can 
readily  be  found. 

Somewhat  extensive  progeny  tests  have  been  made  for  five  of  the 
mutant  types,  and  a  little  evidence  secured  for  two  Or  three  other  types. 


160  University  of  California  Publication*  in  Agricultural  Sciences       [Vol.4 

The  early  type  is  probably  due  to  a  single  dominant  mutant  factor 
segregating  normally  from  the  corresponding  Snowflake  factor;  the 
quantitative  nature  of  its  differences  from  Snowflake.  however,  makes 
positive  determination  of  this  point  a  matter  of  great  difficulty. 

At  least  five  other  types  plainly  reproduce  themselves,  but  about 
50  to  70  per  cent  of  the  progeny  are  usually  Snowflake ;  no  true- 
breeding  individual  of  any  generation  of  any  of  these  types  has  yet 
been  tested.  Genetic  work  with  most  of  these  types  has  been  much 
hampered  or  even  prevented  by  low  vigor  and  fecundity,  and  the 
aggregate  data  from  progeny  of  parents  of  four  types  strongly  indi- 
cate selective  viability  at  germination.  It  has  been  determined  by 
crossing  that  in  three  of  the  types  the  mutant  factor  (or  factors)  is 
carried  both  by  eggs  and  by  sperms.  From  these  facts  it  seems  prob- 
able that  homozygotes  of  the  mutant  types  are  non-viable,  and  that 
severe  selective  elimination  occurs  during  embryonic  development; 
or,  in  other  words,  that  the  mutant  factor  is  imperfectly  recessive  for 
a  lethal  effect. 

In  three  types  there  appears  to  be  linkage  with  the  factor  pair  for 
singleness  and  doubleness  of  flowers,  the  mutant  factor  being  coupled 
with  singleness  in  the  tested  apparent  mutants  of  two  types,  and  with 
doubleness  in  the  third  type.  With  two  other  types  these  factors 
seem  to  be  independent.  No  reversal  of  coupling  has  been  found  in 
later  generations  of  the  former  two  types,  but  on  the  scheme  presented 
crossover  singles  should  be  scarce. 

For  one  type  (crenate-leaved)  a  hypothesis  based  on  the  facts  stated 
gives  very  closely  the  ratio  obtained  from  selfed  parents.  Reciprocal 
crosses  with  Snowflake  conform  less  closely  to  the  requirements  of  the 
hypothesis,  but  do  not  definitely  contradict  it.  The  slender  type, 
which  shows  similar  apparent  linkage,  seems  to  disagree  definitely 
with  the  hypothesis ;  there  is  strong  evidence,  however,  that  slender 
individuals  may  differ  genetically  among  themselves. 

A  more  complex  scheme  providing  also  for  the  usual  origin  of  these 
types  from  Snowflake  by  segregation  is  briefly  outlined. 

The  selfing  ratios  are  very  suggestive  of  duplication  of  a  chromo- 
some (non-disjunction),  as  in  Oenothera  lata,  but  it  is  hard  to 
reconcile  the  cases  of  apparent  linkage  with  this  hypothesis.  It  seems 
probable  that  these  three  linked  types  have  originated  and  are  trans- 
mitted in  the  same  general  way  as  the  double-flowered  type,  and  that 
all  of  these  four  mutant  factors  (including  double)  represent  changes 
of  some  sort  within  a  chromosome  of  the  same  pair,  which  may  be 


Froai :    Mutation  in   tfatth  i  161 

numbered  I      Miss  Saunder's  work  shows  thai  two  flower-color  factors 
also  belong  t<>  this  linked  group. 

The  large  leaved  type  strikingly  resembles  Oenothera  gigas,  and  il 
may  prove  to  be  triploid  in  nuclear  constitution,  In  thai  case  segrega 
tion  maj  be  irregular  and  genotypically  intermediate  individuals  maj 
be  more  or  less  frequentlj   produa  d. 

It  is  probable  thai  further  studj  of  these  types  will  help  to  explain 
tin-  remarkable  genetic  behavior  of  Oenothera  and  of  dints. 


LTTERATl'HK  <  ITHI) 

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Gaz.,  vol.  63,  1917,  pp.  81-82.) 

Muller,  Hermann  J. 

1917.  An  Ocnothcra-like  ease  in  Drosophila.     Nat.  Acad.  Sci.,  Proc,  vol.  3, 

lip.  619-626. 

1918.  Genetic  variability,  twin  hybrids  and  constant  hybrids,  in  a  case  of 

balanced  lethal  factors.    Genetics,  vol.  3,  pp.  422-499',  1  table,  1  fig., 
1  diagr. 

Saunders,  Edith  R. 

1911.     Further  experiments  on  the  inheritance  of  doubleness  and  other  char- 
acters in  stocks.     Jour.   Genetics,  vol.   1,  pp.   303-376,   8  tables. 
1911«.  The  breeding  of  double  flowers.     Fourth  Intern.   Conf.   on    Genetics, 
Proc,  pp.  397-405,  diagr. 
*1913.     Double  flowers.     Roy.  Hort.  Soc,  Jour.,  vol.  38,  pt.  3,  pp.  469-482. 


/  rost:    Mutation  wi   Uatthiola  L63 

L913a.  <  >n  the  mode  of  inheritance  of  certain  characters  in  double-throwing 
stocks.  \  reply.  Zeitschr.  1'.  indukt.  Abstain.-  u.  Vererbungsl.,  vol 
10,  pp.  297  .".I". 

1915.  A  suggested  explanation  of  the  abnormallj    high  records  of  doubles 

quoted  bj  growers  of  stocks  i  Vatthiola) .  Jour.  Genetics,  vol.  5, 
pp.  L37    l  13,  3  tallies. 

1916.  On  selective  partial  steribitj  as  an  explanation  of  the  behavior  of  the 

double-throwing  stock   and   the  petunia.     Am.   Naturalist,   vol.  50, 
pp.  186    198. 
Sin  li.  (ii  ORG]     II. 

1914.  Duplicate  genes  for  capsule  form  in  Bursa  bursa-pastoris.  Zeitschr. 
f.  indukt.  Abstain.-  n.  Vererbungsl.,  vol.  12,  pp.  97-149,  5  tables, 
7  figs. 

v. " 
1908.     The  probable  error  of  a  mean.     Biometrika,  vol.  6,  pp.  1—25,  tables, 
I  diagr. 

1917.  Tables  for  estimating  the  probability  thai  the  mean  of  a  unique  scries 

of  observations  lies  between  —  ~  and  any  given  distance  of  the 
mean  of  the  population  from  which  the  sample  is  drawn.  fin, I., 
vol.    I  1.  ii>.    Ill    117.  tables. 

-    ingle,  Walter  T. 

1911.  Variation  in  first-generation  hybrids  (imperfect  dominance):  its  pus 

sible    explanation    through    zygotaxis.      Fourth    Intern.    Conf.    on 
Genetics,   Proc,  pp.  381-393,    10   figs. 
Tschkkmak.  Erich  vox. 

*1904.     Weitere  Kreuzungsstudien  an  Erbsen,  Levkojen  u.  Bohnen.    Zeitschr. 
f.  d.   landw.   Versuchswesen  in  Oesterreich,  1904,  pp.  533  638. 

1912.  Bastardierungsversuche  an  Erbsen,  Levkojen,  und   Bohnen  mit  Riick- 

sicht  auf  die  Faktorenlehre.  Zeitschr.  f.  indukt.  Abstain.-  a.  Verer- 
bun<:sl.,  vol.  7,  ]ip.  81-234,  tables. 

AVeijbf.r,  Herbert  J. 

1906.  Pedigree  records  used  in  the  plant-breeding  work  of  the  Department 
of  Agriculture,  in  L.  IT.  Bailey,  Plant  Breeding  (New  York,  Mac- 
millan),  pp.  308-31 9. 

DE  VRIES,   HufiO. 

1006.  Species  and  varieties:  their  origin  by  mutation.  Mil.  2,  Chicago,  Open 
Court  Pub.  Co.,  xviii  -1-  847  pages. 

1918.  Twin  hybrids  of  Oenothera  hoolceri  T.  and  G.    Genetics,  vol.  3,  pp.  307- 

421,  14  tables. 
1019.     Oenothera   rubrinervis,   a   half  mutant.     Pot.  Gaz.,  vol.  67,  pp.   1-26, 
tables. 

Yule,  G.  Udnt. 

1911.      An  introduction  to  the  theory  of  statistics.     London,  Charles  Griffin  & 
Co.,  xiii  -+-  3"*'  pa^es,  53  figs. 


PLATE  22 

The  Early  Type 

Fig.  1.  March  20,  1908.  The  single  progeny  of  WG9.  Plants  from  house  M 
to  the  reader's  left  from  stake,  from  house  W  to  right  of  stake,  from  house  C 
below.  WG9-C10,  the  earhr  apparent  mutant,  is  the  middle  plant  in  the  lower 
row.     The  stake  indicates  inches. 

Fig.  2.  About  May  1,  1908.  WG9-C10  at  the  left,  WG9-C9  (Snowflake)  at 
the  right. 


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f  FROST  )    PLATE    22 


Fig.   1 


Fig.   2 


PLATE  23 

The  Early  Type 

Fig.  3.  April  8,  1909.  The  single  progeny  of  WG9-C9  (Snowflake);  arrange- 
ment as  in  figure  1 . 

Fig.  4.  April  9,  1909.  The  single  progeny  of  W69-C10  (heterozygous  early). 
Warm-house  plants  partly  at  right  of  stake  in  lower  row;  arrangement  other- 
wise as  in  figure  3.     Compare  with  figure  3,  house  by  house. 


[166] 


UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


[  FROST  ]    PLATE    23 


Fie.  3 


Pis:,    i 


4 
* 


s 


PLATE  24 

The  Early  Type 

Fig.  5.     July  19,  1911.     Lots  1  to  10,  with  lots  11   to  14  mostly  in  sight  at 
the  right.     Odd-numbered  lot  in  nearer  (west)  half  of  each  row. 

Fig.  6.     July  10,  1911.     Lots  19  to  28,  with  lots  15  to  18  mostly  in  sight  at 
the  left. 


[168] 


UNIV.    CALIF.    PUBL.   AGRI.    SCI.    VOL.    2 


(  FROST  1    PLATE    24 


Fig.  5 


Fig.  6 


PLATE  25 

The  Smooth-leaved  Type 

Fig.  7.     April  27,  1909.     Smooth-leaved   apparent  mutants.     Compare   with 
figures  3  and  4  as  to  earliness,  noting  the  difference  in  date. 

Fig.  8.     May  29,  1914.     Progeny  of  a  smooth-leaved  parent.     Plant  at  right 
Snowflake  single,  the  others  smooth. 


[170] 


UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


[  FROST  |    PLATF.    25 


Fig.    7 


Pig.    8 


PLATE  26 

The  Smooth-leaved  Type 

Fig.  9.     June  28,  1915.     Progeny  of  a  smooth-leaved  parent.     Smooth  single 
at  left,  Snowflake  double  at  right. 

Fig.  10.     Same  date  and  parent  as  with  figure  9.    From  left  to  right:  Snow- 
flake  double  (also  shown  in  figure  9),  Snowflake  single,  smooth  double. 


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Fie.    !> 


Vie.    1(1 


PLATE  27 

The  Large-leaved  Type 

Fig.  11.  August  29,  1914.  Progeny  of  a  large-leaved  parent  (28a),  near 
the  close  of  the  hot  Riverside  summer.  From  left  to  right:  large  single,  large 
double,  Snowflake  single  (two,  the  first  injured  by  aphids). 


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UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


[  FROST  1    PLATE    27 


Fig.    11 


PLATE  28 

The  Large-leaved  Type 

Fig.  12.  July  8,  1916.  Progeny  of  a  large-leaved  parent.  Middle  plant 
Snowflake;  the  rest  large;  all  single. 

Fig.  13.  July  8,  1916.  Progeny  of  a  large-leaved  parent,  more- than  a  month 
older  than  those  shown  in  figure  12.  From  left  to  right:  large  double,  Snow- 
flake  double,  large  single. 


[176] 


UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


[  FROST  ]    PLATE    28 


••       .J    ,  b 


Fie.   L3 


PLATE  29 

The  Crenate-leaved  Type 

Fig.  14.  April  6,  1909.  Crenate-leaved  apparent  mutants.  Note  the  varia- 
tion in  leaf  serration,  and  especially  the  slightness  of  the  serration  (or  crenation) 
with  the  one  cool-house  plant  (below). 

Fig.  15.  April  14,  1911.  Progeny  of  a  crenate-leaved  parent,  grown  in  a 
cool  greenhouse.  The  first  two  plants  at  the  right  are  Snowflake,  the  rest 
crenate. 


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UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


|  FROST  |    PLATE    29 


Fie.    14 


knk-l*^ 

1 

W£ 

jfl 

hn 

1         '  1 '  ■       ■  1 

A    1 

1r 

!      1 

I*7| 

I         1 

J 1  rrvvru-A^. 

]          ^^ 

^^m^^i 

Pie 


PLATE  30 

The  Crenate-leaved  Type 

Fig.  16.     July  8,  1916.     Progeny  of  a  crenate-leaved  parent.     From  left  to 
right:  crenate  single  (two),  crenate  double,  Snowflake  double. 

Fig.  17.     July  8,  1916.    Snowflake  X  crenate-leaved,  F,.    From  left  to  right: 
smooth,  Snowflake  single,  crenate  double  (two). 


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Fie.  n; 


Pie.  1: 


PLATE  31 

The  Slendee  Type 

Fig.  18.  April  27,  1900.  Miscellaneous  aberrant  individuals,  with  two 
typical  Snowflake  plants  (third  from  the  left  above,  second  from  the  left 
below).  In  upper  row:  second  from  left,  narrow  double;  second  from  right, 
slender  double.     In  lower  row  at  left,  slender  single  (25b). 

Fig.  19.  April  14,  1911.  Progeny  of  a  slender  parent  (25b).  Two  at  the 
right  Snowflake,  the  rest  slender. 


[182] 


UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


[  FROST  |    PLATE    31 


L 

L 

P^^V 

^|lj§P^ 

&* 

it* 

yffi 

1* 

*fc^ 

^dgg#fr,  |,    »  aigrfr-  ij 

BB^ 

3 

*■..   *■  ■.  > 

f-A7-0T> 

Fig.   18 


Pie.   1!> 


* 


PLATE  32 

The  Slender  Type 

Fig.  20.     June  3,  1914.     Progeny  of  slender  parents.     From   left  to  right: 
slender  single,  slender  double,  Snowflake  double. 

Fig.  21.     July  7,  1916.     Snowflake   X   slender,  F,.     Middle  plant  Snowflake; 
the  others  slender;  all  single. 


[184] 


UNIV.    CALIF.    PUBL.   AGRI.    SCI.    VOL.    2 


[  FROST  |    PLATE    32 


hi* ' 

■T.-twI      r. 

7v  ■_-.. 

Kwn^ 

K.    "      . 

wg| 

• 

- 

f-A_'- 

i 

1  v 

""^\       ''"— 

Fig.  21 


PLATE  33 

The  Narrow-leaved  Type 

Tig.  22.     April  13,  1911.    Narrow-leaved  apparent  mutants. 

Fig.  23.     June  3,  1914.     A  narrow-leaved  apparent  mutant  among  progeny 
of  a  erenate-leaved  parent.     From  left  to  right:  narrow  double,  erenate  single 

(two). 


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UNIV.    CALIF.    PUBL.    AGRI.    SCI.    VOL.    2 


I  FROST  1    PLATE    33 


Fie.  22 


Pig.  23 


PLATE  34 

The  Narrow-leaved  and  Small-smooth-leaved  Types 

Fig.  24.  June  28,  1915.  A  narrow-leaved  apparent  mutant  among  F,  progeny 
from  Snowflake  X  slender.     Narrow  double  at  left;  the  rest  Snowflake  single. 

Fig.  25.  April  14,  1911.  Miscellaneous  aberrant  plants,  some  being  apparent 
mutants.  From  the  left:  first  and  fifth  small-smooth,  third  stout  dwarf,  seventh 
slender.     See  text. 


[188] 


UNIV.    CALIF.    PUBL.   AGRI.    SCI.    VOL.    2 


[  FROST  I    PLATE    34 


Fig.   24 


Fig.  25 


PLATE  35 
The  Narrow-darkxleaved  Type 

Fig.  26.  June  3,  1914.  A  narrow-dark-leaved  apparent  mutant  among 
progeny  of  a  narrow-leaved  parent.  Third  plant  from  left  narrow-dark  single; 
the  other  three  Snowflake  double. 

Fig.  27.  June  28,  1915.  Progeny  of  a  "small-convex-leaved(?)  "  parent 
(27a).    From  left  to  right:  narrow-dark  single,  Snowflake  double,  smooth  single. 


[190] 


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[  FROST  |    PLATE    35 


■  C 


Pie.  26 


Kiir.  127 


